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Sndgems jewelry guides are easy to use, interesting and helpful guide to buying jewelry onle. Our jewelry guides are indispensable guide to judging jewelry characterstics, distinguishing genuine from imitation, making wise choices, useful to all type of consumers, from professional jewelry to online searchers.  Our diamond guides help everyone in viewing diamonds as gemologists, diamond experts, diamond dealers, experienced lapidaries, diamond buyers and online customers.  Our diamond guides dissects each aspect of diamond value in detail with a wealth of diamond grading information. Our gemstone guides help everyone in viewing colored gemstones as gemologists, gem dealers, experienced lapidaries, gem buyers and online customers.  Our gemstone guides dissects each aspect of ruby, sapphire, ruby value in detail with a wealth of gemstone grading information. Our guides offers step-by-step instructions for how to examine and judge the quality and craftsmanship and materials even if you dont know anything about jewelry.  If you're thinking of buying jewelry online this guide is a best place to start.  Our guides will help you to know about jewelry details such as finishes, settings, flaws and fakes. Our guides cover diamonds, gemstones, jewelry craftsmanship, treatments, diamond and gems sources, appraisals. There is something for everyone.

Gemstones Buying Guides, Expert Advice, Online Gemstone Shopping Tips

Welcome to the dazzling world of gemstones! You will find out all the shiny details about gem stones, what type of gemstones can be found out there and how from dusty hard rocks they transform into that precious shiny ring necklace or pendant in your nearby jewelry store.

Gems have intrigued human beings for more than 10,000 years. This stones were reserved for wealthy and served as status symbols. A prior knowledge of gemstones (ruby, emerald and sapphire) will help you understand and retain what a jeweler tells you. This gemstone guide will help you in evaluating the quality of ruby, emerald and sapphire, an aid in avoiding fraud with information on immitation (synthetic and treatment), as a handy reference on colored gemstones, provide a collection of practical tips on choosing and caring for gems and a challenge to view colored gemstones through the eyes of gemologists and gem dealers. When gemologists speak of shape, they usually mean its face up outline. The most common gemstone shapes include round, oval, square, pears, marquise and octogon.

Precious gems are generally rare and have deep vivid colors. Only three gems are winning candidates for the title of “precious”: the vivid green jade, the deep mysterious blue sapphire and the passionate red ruby. Because natural high quality precious gems are very rare, the jewelry industry will usually use additional chemical processes to enhance the color, clarity of the stones or even synthetically create them so they can be proudly inserted into creative pieces various budgets can buy.

The most precious, worldwide known and desired is of course, the diamond, a symbol for eternal shine and strength and according to popular culture: “a girl’s best friend”. To assess the value of precious gemstones, specialists evaluate according to the so called “4 Cs”: color, cut clarity and carat weight. For colorless diamonds, the cut and the carat weight would be the determining factors in assessing their high value whereas for the other precious gems the quality of their color is one of the most important factors in determining their worth.

Precious gemstones come from all over the world, but there are various regions that are very well known for their precious gem: Brazil is one of the largest exporters of amethysts, certain African countries such as Sierra Leone are well known for the bountiful supply of diamonds and for some economies in the world, precious gem stone trade accounts for almost 30% of their trade volume.

Their rarity and increased value has generated throughout history various mythical interpretations that are associated with each gemstone. From antique beliefs that gems have healing powers to the modern association between one’s birth month and a specific gem there have been numerous mystical accounts people have created to add powerful dimensions to the rarity and preciousness of gems.

Whether you are just dazzled by their beauty, or interested in how they are valued and processed or just intrigued by their mythical stories click on the above tabs for more information!More commonly known as gems, gemstones are pieces of minerals used in the art of making jewelry. They are usually colored, either opaque or transparent and according to their worth gems can be considered precious and semi-precious.

American Gemological Society: Since 1934, American Gem Society (AGS) has been protecting the consumers. For 70 years, the AGS logo has been a symbol of excellence in the jewelry industry. As an association of fine jewelers, our members are committed to the highest ethics, and practice truth-in-advertising and pricing. To visit AGS website click here. AGS is located at 181 World Trade Center, 2050 Stemmons Expressway, Dallas, TX 75027 and their telephone number is 809-972-1162.

Enhancement is often used as another word for treatment. Enhancement also refers to the faceting and polishing of a gem. For centuries, ruby, emerald and sapphire have been in heat treated to improve their color. Heat treating is widely accepted because it is a continuation of a natural process and it causes a permanent improvement of the entire gemstone. From the standpoint of value, it does not matter whether commercially-quality stones have been treated or not as long as the color is permanent. The overall quality of the treated stone will determine the price. However, a premium may be charged for high-quality untreated stones that comes with a lab report stating there is no evidence of heat treatment.

  • The "celestial" sapphire, symbol of the heavens, bestower of innocence, truth, good health, and preserver of chastity, is reserved today as the birthstone of September.

    Sapphire was named after the Greek word "sapphirus", meaning blue. The striking deep blue of a quality sapphire is reminiscent of a cloudless night sky.  Ancient civilizations believed that the world was set upon an enormous sapphire, which painted the sky blue with its reflection. In ancient times, Sapphires were thought to be protective against envy, and even against poisoning.  A common belief was that a venomous snake placed in a Sapphire vessel would rapidly die!  Ground to a powder, the blue stone was believed to cure colic, rheumatism and mental illness, and to strengthen eyesight.

    Sapphire has long symbolized truth, sincerity, and faithfulness. The Tradition holds that Moses was given the ten commandments on tablets of sapphire, making it the most sacred gemstone. Because sapphires represent divine favor, they were the gemstone of choice for kings and high priests. The British Crown Jewels are full of large blue sapphires, and even more recently Prince Charles chose a sapphire engagement ring for Princess Diana. The ancients regarded star sapphires as a very powerful talisman, a guiding star for travelers and seekers of all kinds.

    The word "ruby" derives from the Latin word rubeus, which means red. Ruby is the name given to the red variety of corundum.

    The word Ruby comes from the Latin "ruber," meaning red..It has been said that the Ruby's red glow comes from an internal flame that cannot be extinguished, making a gift of this stone symbolic of everlasting love.  With its hardness and durability, it is a perfect engagement gem.  And if worn on the left hand, ancient lore has it that the Ruby will bring good fortune to its wearer, too! Ruby has been the world's most valued gemstone for thousands of years. Ruby was said to be the most precious of the twelve stones God created when he created all things, and this "lord of gems" was placed on Aaron's neck by God's command.

    In the Bible, Job says that �wisdom is more precious than rubies� Rubies were thought to represent heat and power.  Ancient tribes used the gem as bullets for blowguns, and it was said that a pot of water would boil instantly if a Ruby was tossed into it.  Ground to powder and placed on the tongue, this crystal was used as a cure for indigestion. Among the multitude of legends and strange beliefs of ancient times, it was thought that the wearer of a ruby was blessed with health, wealth, wisdom and outstanding success in`heart affairs '.Furthermore, the wearer acquired the ability to live in peace with his enemies. In some places ruby was even thought to confer invulnerability. Rubies are today even more valuable and rare than the top quality colorless diamonds. A 16 carat ruby was sold at auction for US$ 227,300 per carat at Sotheby's in 1988.

    The name emerald is a derivative of an ancient Persian word, coming to us through the corruption of the Latin `Smaragdus'. The history of the emerald is as fascinating as it is voluminous. The ancients prized it as the symbol of love, rebirth and eternal youth. Because the rich green color of emerald reminds of spring, it has been treasured for at least the past 4,000 years by different cultures all around the world. Cleopatra reportedly valued her emeralds more than any other gem, and with good cause as the ancient Egyptians revered them as symbols of fertility and rebirth.

    The Romans believed that emeralds with a pale hue were immature and would grow to a deeper, richer colour with age. The ancient Roman scholar Pliny was so moved by the emerald's lush colour he wrote, �nothing is more intense than the green of emerald� and �sight is refreshed and restored by gazing upon this stone�. Following his advise, Roman emperor Nero wore emerald sunglasses to watch the gladiators. Emerald is said to give a supernatural ability to foretell future events. A surprising variety of virtues have been ascribed to emerald. Among these, emerald was thought to improve its owner�s memory and eloquence, and was also said to quicken intelligence. In a particular instance of emerald�s use, as a measure against ills, women wearing the stone were believed to be immune from epilepsy.

    Shape of Gemstone

    The facet gemstone have several shapes. Some is normal but some shapes can not be found in normal gem market because some shape is cut from the imagine of cutter. It is mean that is the unique shape. But the gemstone and diamond shapes chart below is the standard shapes that offer in gem market around the world.

    Gemstone and diamonds shapes

    Emerald cut

    Emerald cut is a rectangular or square step cut with diagonal corners. It has approximately 50 facets.

    Oval cut

    Oval cut is a modified brilliant cut with an obround shaped girdle outline. The oval cut has an elliptical shape when viewed from the top. It has approximately 69 facets.

    Radiant cut

    Radiant cut is a rectangular cut, combining the shape of an emerald cut and sparkle of a brilliant. It has approximately 70 facets.

    Pear or Teardrop cut

    Pear or Teardrop cut is asymmetrical cut with one pointed and one rounded end. A hybrid cut, combining the best of the oval and the marquise, it is shaped like a sparkling teardrop. It has approximately 71 facets.

    Cushion cut

    Cushion cut is looks like a cross between a deep cut with large facets that was common in the late 19th and the early 20th centuries and a modern

    Marquise cut

    Marquise cut is a symmetrical boat shaped brilliant cut gem with pointed ends. It has approximately 57 facets.

    Old miner cut

    Old miner cut is also more of a square or cushion cut, rather than being round. In fact, today's cushion cut is an improved old mine cut.

    Trillion cut

    Trillion cut is a triangular shape. It has approximately 44 facets.

    Heart cut

    Heart cut is a pear shape with a cleft at the top. It has approximately 59 facets.

    Asscher cut

    Asscher cut is a square cut characterized by a smaller table and larger step facet than an emerald cut.

    Flanders cut

    Flanders cut is an octagon, but when viewed from above it looks like a square. In reality it has four short sides and four long sides. This cut also includes 61 facets

    Princess cut

    Princess cut is technically known as “Square Modified Brilliant” and is a square version of the round brilliant cut with numerous sparkling facets. It has approximately 76 facets.

    Round cut

    Round cut is the name implies, it is round on top. It has approximately 57 facts.

    Gemstones Specific Gravity, Mohs Hardness, Index of Refraction

    Learn all about gemstones properties like Specific Gravity, Mohs Hardness, Index of Refraction as it will help in identifying genuine gemstone from fake stones, evaluating gemstone quality and source of origin.

    Gemstone Name Specific Gravity Mohs Hardness Index of Refraction Gemstone Family
    Achorite 3.03 - 3.25 7.0 - 7.5 Mohs 1.610-1.661 Tourmaline
    Agate 2.65 7.0 Mohs 1.530 - 1.550 Quartz
    Alexandrite 3.68 - 3.78 8.5 Mohs 1.746 - 1.755 Chrysoberyl
    Almandine 3.50 - 4.30 6.5 - 7.5 Mohs 1.750 - 1.830 Garnet
    Almandine Spinel 3.58 - 4.06 8.0 Mohs 1.708 - 1.735 Spinel
    Almandine-Spessartine 3.50 - 4.30 6.5 - 7.5 Mohs 1.750 - 1.830 Garnet
    Amazonite 2.55 - 2.76 6.0 - 6.5 Mohs 1.518 - 1.526 Feldspar
    Amethyst 2.65 7.0 Mohs 1.532 - 1.554 Quartz
    Andradite 3.50 - 4.30 6.5 - 7.5 Mohs 1.880 - 1.940 Garnet
    Aquamarine 2.63 - 2.91 7.5 - 8.0 Mohs 1.567-1.590 Beryl
    Balas Ruby 3.58 - 4.06 8.0 Mohs 1.708 - 1.735 Spinel
    Black Opal 1.98 - 2.25 5.5 - 6.5 Mohs 1.440 - 1.460 Opal
    Bloodstone 2.65 7.0 Mohs 1.535 - 1.539 Quartz
    Brazilian Emerald 3.03 - 3.25 7.0 - 7.5 Mohs 1.610 - 1.640 Tourmaline
    Cairngorm 2.65 7.0 Mohs 1.540 - 1.550 Quartz
    Carnelian 2.65 7.0 Mohs 1.530 - 1.550 Quartz
    Cat's Eye 3.68 - 3.78 8.5 Mohs 1.746 - 1.755 Chrysoberyl
    Chalcedony 2.65 7.0 Mohs 1.544 - 1.553 Quartz
    Chlorspinel 3.58 - 4.06 8.0 Mohs 1.712 - 1.717 Spinel
    Chrome Pyrope 3.50 - 4.30 6.5 - 7.5 Mohs 1.730 - 1.760 Garnet
    Chrysoberyl 3.68 - 3.78 8.5 Mohs 1.746 - 1.755 Chrysoberyl
    Chrysoprase 2.65 7.0 Mohs 1.530 - 1.550 Quartz
    Citrine 2.65 7.0 Mohs 1.532 - 1.554 Quartz
    Color-Change Garnet 3.50 - 4.30 6.5 - 7.5 Mohs 1.730 - 1.760 Garnet
    Demantoid 3.50 - 4.30 6.5 - 7.5 Mohs 1.880 - 1.900 Garnet
    Diamond 3.51 10 Mohs 2.417 Diamond
    Dravite 3.03 - 3.25 7.0 - 7.5 Mohs 1.610-1.661 Tourmaline
    Emerald 2.63 - 2.91 7.5 - 8.0 Mohs 1.560 - 1.605 Beryl
    Feldspar 2.55 - 2.76 6.0 - 6.5 Mohs 1.518 - 1.572 Feldspar
    Fire Opal 1.98 - 2.25 5.5 - 6.5 Mohs 1.430 - 1.460 Opal
    Garnet 3.50 - 4.30 6.5 - 7.5 Mohs 1.730 - 1.760 Garnet
    Ghanospinel 3.58 - 4.06 8.0 Mohs 1.712 - 1.747 Spinel
    Goshenite 2.63 - 2.91 7.5 - 8.0 Mohs 1.570 - 1.600 Beryl
    Green Quartz 2.65 7.0 Mohs 1.540-1.550 Quartz
    Grossular 3.50 - 4.30 6.5 - 7.5 Mohs 1.880 - 1.940 Garnet
    Heliodore 2.63 - 2.91 7.5 - 8.0 Mohs 1.570 - 1.600 Beryl
    Heliotrope 2.65 7.0 Mohs 1.535 - 1.539 Quartz
    Hessonite 3.50 - 4.30 6.5 - 7.5 Mohs 1.730 - 1.760 Garnet
    Hyacinth 4.60 - 4.70 7.5 Mohs 1.777 - 1.987 Zircon
    Indicolite 3.03 - 3.25 7.0 - 7.5 Mohs 1.610 - 1.640 Tourmaline
    Jade 2.90 - 3.10 6.0 Mohs 1.640 - 1.667 Jade
    Jadeite 2.90 - 3.10 6.0 Mohs 1.640 - 1.667 Jade
    Jargon 4.60 - 4.70 7.5 Mohs 1.777 - 1.987 Zircon
    Jasper 2.65 7.0 Mohs 1.540 - 1.550 Quartz
    Labradorite 2.55 - 2.76 6.0 - 6.5 Mohs 1.560 - 1.572 Feldspar
    Lapis Lazuli 2.70 - 2.90 5.0 - 5.5 Mohs 1.500 - 1.550 Lapis Lazuli
    Malaia 3.50 - 4.30 6.5 - 7.5 Mohs 1.880 - 1.940 Garnet
    Matura Diamond 4.60 - 4.70 7.5 Mohs 1.777 - 1.987 Zircon
    Moonstone 2.55 - 2.76 6.0 - 6.5 Mohs 1.518 - 1.526 Feldspar
    Morganite 2.63 - 2.91 7.5 - 8.0 Mohs 1.585 - 1.594 Beryl
    Morion 2.65 7.0 Mohs 1.540 - 1.550 Quartz
    Nephrite 2.90 - 3.10 6.0 Mohs 1.600 - 1.641 Jade
    Onyx 2.65 7.0 Mohs 1.531 - 1.539 Quartz
    Opal 1.98 - 2.25 5.5 - 6.5 Mohs 1.440 - 1.460 Opal
    Orthoclase 2.55 - 2.76 6.0 - 6.5 Mohs 1.518 - 1.526 Feldspar
    Peridot 3.22 - 3.45 7.0 Mohs 1.635 - 1.690 Peridot
    Peristerite 2.55 - 2.76 6.0 - 6.5 Mohs 1.560 - 1.572 Feldspar
    Praziolite 2.65 7.0 Mohs 1.540 - 1.550 Quartz
    Pyrope 3.50 - 4.30 6.5 - 7.5 Mohs 1.730 - 1.760 Garnet
    Pyrope-Almandine 3.50 - 4.30 6.5 - 7.5 Mohs 1.730 - 1.760 Garnet
    Pyrope-Spessartine 3.50 - 4.30 6.5 - 7.5 Mohs 1.730 - 1.760 Garnet
    Quartz 2.65 7.0 Mohs 1.544 - 1.553 Quartz
    Red Beryl 2.63 - 2.91 7.5 - 8.0 Mohs 1.570 - 1.598 Beryl
    Rhodolite 3.50 - 4.30 6.5 - 7.5 Mohs 1.740 - 1.770 Garnet
    Rock Crystal 2.65 7.0 Mohs 2.000 Quartz
    Rose Quartz 2.65 7.0 Mohs 1.540 - 1.550 Quartz
    Rubellite 3.03 - 3.25 7.0 - 7.5 Mohs 1.610 - 1.640 Tourmaline
    Rubicelle 3.58 - 4.06 8.0 Mohs 1.712 - 1.717 Spinel
    Ruby 3.96 - 4.05 9.0 Mohs 1.757 - 1.779 Corundum
    Sapphire 3.96 - 4.05 9.0 Mohs 1.757 - 1.779 Corundum
    Sapphire Spinel 3.58 - 4.06 8.0 Mohs 1.712 - 1.747 Spinel
    Siberite 3.03 - 3.25 7.0 - 7.5 Mohs 1.625-1.675 Tourmaline
    Smoky Quartz 2.65 7.0 Mohs 1.540 - 1.550 Quartz
    Spessartine 3.50 - 4.30 6.5 - 7.5 Mohs 1.790 - 1.810 Garnet
    Spinel 3.58 - 4.06 8.0 Mohs 1.712 - 1.717 Spinel
    Sunstone 2.55 - 2.76 6.0 - 6.5 Mohs 1.560 - 1.572 Feldspar
    Topaz 3.50 - 3.60 8.0 Mohs 1.607 - 1.627 Topaz
    Topazolite 3.50 - 4.30 6.5 - 7.5 Mohs 1.880 - 1.940 Garnet
    Tourmaline 3.03 - 3.25 7.0 - 7.5 Mohs 1.603 - 1.655 Tourmaline
    Tsavorite 3.50 - 4.30 6.5 - 7.5 Mohs 1.739 - 1.744 Garnet
    Turquoise 2.60 - 2.80 5.0 - 6.0 Mohs 1.610 - 1.650 Turquoise
    Uvarovite 3.50 - 4.30 6.5 - 7.5 Mohs 1.740 - 1.870 Garnet
    Verdilite 3.03 - 3.25 7.0 - 7.5 Mohs 1.612-1.638 Tourmaline
    Water Opal 1.98 - 2.25 5.5 - 6.5 Mohs 1.440 - 1.460 Opal
    White Opal 1.98 - 2.25 5.5 - 6.5 Mohs 1.440 - 1.460 Opal
    Zircon 4.60 - 4.70 7.5 Mohs 1.777 - 1.987 Zircon

    Gemstone's specific gravity

    Specific gravity, the abbreviated is SG, is the meatured that comparing about the gemstone's weight when weighted in the air with weighted suspennded in pure water. Because specific gravity varies with chemical composition and crystal structure type.The specific gravity is a ratio which can be used for indentifying gemstones. But this method can not be used for identified gemstone alone. But the specific gravity can help in reducing the amount kind of gemstone of possibilities. Learn all about gemstones properties like Specific Gravity, Chemical Composition and Crystal Stucture as it will help in identifying genuine gemstone from fake stones, evaluating gemstone quality and source of origin.

    The table below is the list gemstone's specifict gravity that arranged from the gemstone in increasing order.

    Gemstone type

    Specific gravity

    Chemical Composition

    Crystal Structure

    Amber

    1.05 – 1.10

    Oxygenated hydrocarbon (variable)

    Amorphous

    Chrysocolla

    1.9 – 2.4

    Hydrous copper silicate

    Monoclinic

    Opal ex. Fire opal, Moss opal, Doublet opal and Boulder opal

    1.98 – 2.5

    Hydrous silicon dioxide

    Amorphous

    Hackmanite

    2.14 – 2.40

    Sodium aluminum silicate chloride

    Cubic

    Sodalite

    2.14 – 2.40

    Sodium aluminum silicate chloride

    Cubic

    Tourmaline ex. Rubellite, Paraiba, Chrome etc.

    2.28 – 3.32

    Silicate compounded with aluminium, iron, magnesium, sodium, lithium, or potassium.

    Trigonal

    Turquoise

    2.31 – 2.84

    Hydrated copper aluminum phosphate

    Triclinic

    Moldavite

    2.32 – 2.38

    Silicon dioxide + aluminum oxide

    Amorphous

    Hambergite

    2.35

    Beryllium borate

    Orthorhombic

    Obsidian

    2.35 – 2.60

    Siliceous glassy rock

    Amorphous

    Variscite

    2.42 – 2.58

    Hydrous aluminum phosphate

    Orthorhombic

    Serpentine

    2.44 – 2.62

    Basic magnesium silicate

    Microcrystalline

    Howlite

    2.45 – 2.58

    Calcium borosilicate hydroxide

    Monoclinic

    Lapis lazuli

    2.5 - 3

    Sodium calcium aluminum silicate

    Cubic

    Maw sit sit

    2.5 – 3.5

    Rock containing variable amounts of kosmochlor, jadeite and albite

    Rock

    Jasper

    2.5 – 2.9

    Silicon dioxide

    Trigonal

    Charoite

    2.54 – 2.78

    Complex silicate containing phosphorus, calcium, and sodium

    Monochinic

    Seraphinite

    2.55 – 2.75

    Magnesium iron aluminum silicate hyroxide

    Monochinic

    Amazonite

    2.56 – 2.58

    Potassium aluminum silicate

    Triclinic

    Orthoclase

    2.56 – 2.58

    Potassium aluminum silicate

    Monochinic

    Moonstone

    2.56 – 2.59

    Potassium aluminum silicate

    Monochinic

    Scapolite

    2.57 – 2.74

    Sodium calcium aluminium silicate

    Tetragonal

    Chrysophase

    2.58 – 2.64

    Silicon dioxide

    Trigonal

    Bloodstone

    2.58 – 2.64

    Silicon dioxide

    Trigonal

    Agate & Carnelian

    2.58 – 2.64

    Silicon dioxide

    Trigonal

    Peanut wood

    2.58 – 2.91

    Silicon dioxide

    Trigonal

    Rose quartz cat’s eye

    2.58 – 2.64

    Silicon dioxide

    Hexagonal

    Chalcedony

    2.58 – 2.64

    Silicon dioxide

    Trigonal

    Tiger’s eye

    2.58 – 2.64

    Silicon dioxide

    Trigonal

    Iolite

    2.58 – 2.66

    Magnesium aluminum silicate

    Orthorhombic

    Coral

    2.6 – 2.7

    Calcium carbonate

    Trigonal

    Pietersite

    2.6

    Silicon dioxide

    Aggregate

    Fossil coral

    2.6 – 2.7

    Silicon dioxide

    Trigonal

    Agate geode

    2.6 – 2.64

    Silicon dioxide

    Trigonal

    Pearl

    2.6 – 2.85

    Calcium carbonate

    Orthorhombic

    Sunstone

    2.62 – 2.65

    Sodium calcium aluminium silicate

    Triclinic

    Aventurine

    2.64 – 2.69

    Silicon dioxide

    Trigonal

    Quartz

    2.65

    Silicon dioxide

    Trigonal

    Strawberry quartz

    2.65

    Silocon dioxide with iron oxide inclusions

    Trigonal

    Amethyst

    2.65

    Silicon dioxide

    Trigonal

    Quartz ex. Rose, Smoky, Cat’s eye and Mystic

    2.65

    Silicon dioxide

    Trigonal

    Labradorite

    2.65 – 2.75

    Sodium calcium aluminum silicate

    Triclinic

    Citrine

    2.65

    Silicon dioxide

    Hexagonal

    Rutile quartz

    2.65

    Silicon dioxide with titanium inclusions

    Trigonal

    Ametrine

    2.65

    Silicon dioxide

    Trigonal

    Onyx

    2.65 – 2.91

    Silicon dioxide

    Trigonal

    Andesine labradorite

    2.66 – 2.68

    Sodium calcium aluminum silicate

    Triclinic

    Beryl ex. Morganite, Goshenite etc

    2.66 – 2.87

    Aluminium beryllium silicate

    Hexagonal

    Emerald

    2.66 – 2.87

    Aluminium beryllium silicate

    Hexagonal

    Aquamarine

    2.66 – 2.87

    Aluminium beryllium silicate

    Hexagonal

    Calcite

    2.69 – 2.71

    Calcium carbonate

    Trigonal

    Larimar

    2.74 – 2.88

    Hydrated sodium calcium silicate with manganese

    Triclinic

    Ammolite

    2.75 – 2.80

    Mainly aragonite (with calcite, silica and pyrite)

    Amorphous

    Sugilite

    2.76 – 2.80

    Potassium sodium lithium iron manganese aluminium

    Hexagonal

    Verdite

    2.76 - 3

    Serpentine rock

    Monoclinic

    Lepidolite

    2.8 – 2.9

    Potassium lithium aluminum silicate hydroxide fluo

    Monoclinic

    Prehnite

    2.82 – 2.94

    Basic calcium aluminum silicate

    Orthorhombic

    Jadeite

    2.90 – 3.03

    Basic calcium magnesium iron silicate

    Monoclinic

    Nephrite jade

    2.9 – 3.03

    Calcium magnesium iron silicate

    Monoclinic

    Danburite

    2.97 – 3.03

    Calcium boric silicate

    Orthorhombic

    Nuumite

    3

    Rock containing gedrite and anthophyllite

    Lamellar fibrous structure

    Fluorite

    3 – 3.25

    Calcium fluoride

    Cubic

    Andalusite

    3.05 – 3.20

    Aluminium silicate

    Orthorhombic

    Clinohumite

    3.13 – 3.75

    Magnesium silicate

    Monoclinic

    Spodumene ex. Kunzite

    3.15 – 3.21

    Lithium aluminum silicate

    Monoclinic

    Apatite

    3.16 – 3.23

    Basic fluoro- and chloro-calicum phosphate

    Hexagonal

    Hiddenite

    3.17 – 3..19

    Lithium aluminum silicate

    Monoclinic

    Diopsie ex. Chrome, Tashmarine and star

    3.22 – 3.38

    Calcium magnesium silicate

    Monoclinic

    Sillimanite

    3.23

    Aluminum silicate

    Orthorhombic

    Malachite

    3.25 – 4.10

    Basic copper carbonate

    Monoclinic

    Dumortierite quartz

    3.26 – 3.41

    Aluminum borate silicate intergrown with quartz

    Orthorhombic

    Axinite

    3.26 – 3.360

    Calcium aluminum borate silicate

    Triclinic

    Peridot

    3.28 – 3.48

    Magnesium iron silicate

    Orthorhombic

    Hemimorphite

    3.3 – 3.5

    Hydrous basic zinc silicate

    Orthorhombic

    Diaspore or Zultanite

    3.30 – 3.39

    Hydrated aluminum oxide

    Orthorhombic

    Idocrase

    3.32 – 3.47

    Complex calcium aluminum silicate

    Tetragonal

    Ruby - Zoisite

    3.35

    Rock containing zoisite, ruby and hornblende

    Orthorhombic

    Tanzanite

    3.35

    Calcium aluminium silicate

    Orthorhombic

    Rhodonite

    3.40 – 3.74

    Manganese silicate

    Triclinic

    Rhodochrosite

    3.45 – 3.70

    Manganese carbonate

    Trigonal

    Topaz ex. Rutile, Mystic, Azotic, imperial etc.

    3.49 – 3.57

    Aluminum fluorsilicate

    Orthorhombic

    Sphene

    3.52 – 3.54

    Calcium titanium silicate

    Monoclinic

    Kyanite

    3.53 – 3.70

    Aluminum silicate

    Triclinic

    Spinel

    3.54 – 3.63

    Magnesium aluminium oxide

    Cubic

    Grossular garnet ex. Grossularite and Mali

    3.57 – 3.73

    Calcium aluminum silicate

    Cubic

    Tsavorite Garnet

    3.57 – 3.73

    Calcium aluminum silicate

    Rhombic

    Garnet ex. Pyrope and Color Change Garnet

    3.62 – 3.87

    Magnesium aluminum silicate

    Cubic

    Star garnet

    3.62 – 3.87

    Iron aluminum silicate

    Rhombic

    Hessonite Garnet

    3.64 – 3.69

    Calcium aluminum silicate

    Cubic

    Demantoid Garnet

    3.7 – 4.1

    Calcium iron silicate

    Cubic

    Melanite

    3.7 – 4.1

    Calcium iron silicate

    Cubic

    Chrysoberyl

    3.70 – 3.78

    Beryllium aluminium oxide

    Orthorhombic

    Alexandrite

    3.70 – 3.78

    Beryllium aluminium oxide

    Orthorhombic

    Azurite

    3.7 – 3.9

    Basic Copper Carbonate

    Monoclinic

    Gaspeite

    3.71

    Nickel magnesium iron carbonate

    Trigonal

    Rhodolite Garnet

    3.85

    Magnesium aluminum silicate

    Cubic

    Sphalerite

    3.9 – 4.1

    Zinc sulphide

    Cubic

    Almandite Garnet

    3.93 – 4.30

    Iron aluminium silicate

    Cubic

    Zircon

    3.93 – 4.73

    Zirconium silicate

    Tetragonal

    Sapphire

    3.95 – 4.03

    Aluminium oxide

    Trigonal

    Ruby

    3.97 – 4.05

    Aluminum oxide

    Trigonal

    Smithsonite

    4.00 – 4.65

    Zinc carbonate

    Trigonal

    Spessartite Garnet

    4.12 – 4.18

    Manganese aluminium silicate

    Cubic

    Rainbow pyrite

    5 – 5.2

    Iron sulphide

    Cubic

    Hematite

    5.12 – 5.28

    Iron oxide

    Trigonal

    Cassiterite

    Gemstone's Refractive Index

    Refracive index, the abbreviated is RI, is one of the most important identified of gemstone. Because almost gemstones will have different refractive index, but not all. So if you have to make sure what stone you test, you have to used other method with also. Whatever the refractive index testing have to be the one method you can not deny.

    When light passes from one density or type of material (air) into another (the gemstone), it is bent or "refracted." The amount, or degree, that the beam of light is bent will be determined by the density difference between the air and the gem. The measurement used to quantify the amount that a light beam is bent in a given material is known as its "refractive index".

    There are two factors when calculating a gem's refractive index: "angle of incident" and "refractive angle." The "incident angle" is the angle of the approaching light as it intersects with the stone's exterior surface. The "refractive angle" is the altered angle of the light as it passes through the stone's interior. The Refractive Index is the ratio of difference between these two angles. Each material has its own unique density and Refractive Index.

    The color of a gemstone, and the frequency (color) of the light traveling through it, can also effect its refractive index. As the light's frequency changes, so does its angle of refraction. Higher light frequencies travel through the stone more slowly, while lower frequencies travel faster, causing a spreading effect known as dispersion. As each frequency is reflected it is dispersed throughout the stone's interior at varying speeds and directions. As the scattering and dispersion of light within the stone is increased, so to is the amount of "fire" that is returned to the viewer.

    The color of a gemstone, and the frequency (color) of the light traveling through it, can also effect its refractive index. As the light's frequency changes, so does its angle of refraction. Higher light frequencies travel through the stone more slowly, while lower frequencies travel faster, causing a spreading effect known as dispersion. As each frequency is reflected it is dispersed throughout the stone's interior at varying speeds and directions. As the scattering and dispersion of light within the stone is increased, so to is the amount of "fire" that is returned to the viewer. Learn all about gemstones properties like Refractive Index, Double Refraction, Birefringence as it will help in identifying genuine gemstone from fake stones, evaluating gemstone quality and source of origin.

    The table below is the list gemstone's RI that arranged from the gemstone that have the lowest refractive index to highest refractive index.

    Gemstone

    Refractive index

    Double Refraction

    Birefringence

    Opal

    1.37 – 1.52

    None

    N/A

    Fluorite

    1.434

    None

    N/A

    Obsidian

    1.45 – 1.55

    None

    N/A

    Chrysocolla

    1.469 – 1.57

    Yes

    0.023 -  0.040

    Moldavite

    1.48 – 1.54

    None

    N/A

    Sodalite

    1.48

    None

    N/A

    Hackmanite

    1.48

    None

    N/A

    Calcite

    1.486 – 1.658

    Yes

    0.172

    Coral

    1.486 – 1.658

    Yes

    White and red : 0.160 – 0.172

    Lapis lazuli

    1.5

    None

    N/A

    Moonstone

    1.518 – 1.526

    Yes

    0.008

    Orthoclase

    1.518 – 1.53

    Yes

    0.008

    Ammolite

    1.52 – 1.68

    Yes

    0.155

    Pearl

    1.52 – 1.69

    Yes

    0.156

    Maw sit sit

    1.52 – 1.74

    Yes

    0.015 – 0.02

    Amazonite

    1.522 – 1.530

    Yes

    0.008

    Lepidolite

    1.525 – 1.586

    Yes

    0.029 – 0.038

    Sunstone

    1.525 – 1.548

    Yes

    0.010

    Agate

    1.53 – 1.54

    Yes

    0.001 – 0.004

    Bloodstone

    1.53 – 1.54

    Yes

    0.001 – 0.004

    Carnelian

    1.53 – 1.54

    Yes

    0.001 – 0.004

    Quartz ex. Rose, Smoky and Lemon

    1.53 – 1.54

    Yes

    0.009

    Fossil coral

    1.53 – 1.54

    Yes

    0.001 – 0.004

    Chrysophase

    1.53 – 1.54

    Yes

    0.004 – 0.009

    Chalcedony

    1.53 – 1.54

    Yes

    0.001 – 0.004

    Tiger’s eye

    1.534 – 1.540

    None

    N/A

    Quartz cat’s eye

    1.534 – 1.540

    None

    N/A

    Amber

    1.539 – 1.545

    None

    N/A

    Scapolite

    1.540 – 1.579

    Yes

    0.006 – 0.037

    Peanut wood

    1.54

    None

    N/A

    Jasper

    1.54

    None

    N/A

    Iolite

    1.542 – 1.578

    Yes

    0.008 – 0.012

    Aventurine

    1.53 – 1.54

    Yes

    0.009

    Pietersite

    1.544 – 1.553

    Yes

    0.009

    Ametrine

    1.544 – 1.553

    Yes

    0.009

    Mystic quartz

    1.544 – 1.553

    Yes

    0.009

    Onyx

    1.544 – 1.553

    Yes

    0.001 – 0.004

    Rutile quartz

    1.544 – 1.553

    Yes

    0.009

    Amethyst

    1.544 – 1.553

    Yes

    0.009

    Citrine

    1.544 – 1.553

    Yes

    0.009

    Charoite

    1.550 – 1.561

    Yes

    0.004 – 0.009

    Andesine labradorite

    1.551 – 1.560

    Yes

    0.008

    Verdite

    1.552 – 1.576

    None

    N/A

    Hambergite

    1.553 – 1.628

    Yes

    0.007

    Labradorite

    1.559 – 1.570

    Yes

    0.008 – 0.010

    Serpentine

    1.560 – 1.710

    Yes

    0.008 – 0.014

    Morganite

    1.562 – 1.602

    Yes

    0.004 – 0.010

    Beryl

    1.562 – 1.620

    Yes

    0.004 – 0.010

    Goshenite

    1.562 – 1.620

    Yes

    0.004 – 0.010

    Veriscite

    1.563 – 1.594

    Yes

    0.031

    Aquamarine

    1.564 – 1.596

    Yes

    0.004 – 0.005

    Emerald

    1.565 – 1.602

    Yes

    0.006

    Seraphinite

    1.576 – 1.599

    Yes

    0.005 – 0.011

    Howlite

    1.586 – 1.605

    Yes

    0.019

    Larimar

    1.595 – 1.645

    Yes

    0.038

    Rhodochrosite

    1.6 – 1.82

    Yes

    0.208 – 0.220

    Nephrite jade

    1.600 – 1.627

    Yes

    0.027

    Jadeite

    1.600 – 1.627

    Yes

    0.027

    Sugilite

    1.607 – 1.611

    Yes

    0.001 – 0.004

    Topaz

    1.609 – 1.643

    Yes

    0.008 – 0.016

    Gaspeite

    1.61 – 1.81

    Yes

    0.22

    Turquoise

    1.61 – 1.65

    Yes

    0.04

    Prehnite

    1.611 – 1.699

    Yes

    0.021 – 0.039

    Hemimorphite

    1.614 – 1.636

    Yes

    0.022

    Tourmaline ex. Chrome, cat’s eye, rubellite, Paraiba and indicolite

    1.614 – 1.666

    Yes

    0.014 – 0.032

    Smitsonite

    1.621 – 1.849

    Yes

    0.228

    Andalusite

    1.627 – 1.649

    Yes

    0.007 – 0.013

    Apatite

    1.628 – 1.649

    Yes

    0.002 – 0.006

    Clinohumite

    1.629 – 1.674

    Yes

    0.029 – 0.045

    Danburite

    1.630 – 1.636

    Yes

    0.006 – 0.008

    Peridot

    1.650 – 1.703

    Yes

    0.036 – 0.038

    Malachite

    1.655 – 1.909

    Yes

    0.254

    Silimanite

    1.655 – 1.684

    Yes

    0.014 – 0.021

    Axinite

    1.656 – 1.704

    Yes

    0.010 – 0.012

    Spodumene ex. Kunzite, Hiddenite

    1.660 – 1.681

    Yes

    0.014 – 0.016

    Diopside ex. Chrome, star and Tashmarine

    1.664 – 1.730

    Yes

    0.024 – 0.031

    Dumotierite quartz

    1.678 – 1.689

    Yes

    0.015 – 0.037

    Ruby - Zoisite

    1.691 – 1.700

    Yes

    0.009

    Tanzanite

    1.691 – 1.700

    Yes

    0.009

    Idocrase

    1.700 – 1.732

    Yes

    0.002 – 0.012

    Diaspore or refer to Zultanite

    1.702 – 1.750

    Yes

    0.048

    Kyanite

    1.710 – 1.734

    Yes

    0.015 – 0.033

    Spinel

    1.712 – 1.762

    Rhodonite

    1.716 – 1.752

    Yes

    0.010 – 0.014

    Azurite

    1.720 – 1.848

    Yes

    0.108 – 0.110

    Garnet ex. Pyrote, Star, Rhodolite, Color change and Hessonite

    1.720 – 1.756

    None

    N/A

    Grossular garnet ex. Tsavorite, Grossularite and Mali

    1.734 – 1.759

    None

    N/A

    Chrysoberyl

    1.746 – 1.763

    Yes

    0.004 – 0.010

    Alexandrite

    1.746 – 1.763

    Yes

    0.004 – 0.010

    Corundum ex. Sapphire, Ruby

    1.762 – 1.778

    Yes

    0.008

    Garnet ex. Almandite and Spessartite

    1.77 – 1.82

    None

    N/A

    Zircon

    1.810 -2.024

    Yes

    0.002 – 0.059

    Sphene

    1.843 – 2.110

    Yes

    0.100 – 0.192

    Melanite

    1.88 – 1.94

    None

    N/A

    Andradrite garnet ex. Demantoid and Topazolite

    1.88 – 1.94

    None

    N/A

    Cassiterite

    1.997 – 2.098

    Yes

    0.096 – 0.098

    Sphalerite

    2.368 – 2.371

    None

    N/A

    Diamond

    2.417 – 2.419

    None

    N/A

    Hematite

    2.94 – 3.22

    Yes

    0.287

    Learn all about gemstones properties like Clarity as it will help in identifying genuine gemstone from fake stones, evaluating gemstone quality and source of origin.

    Gemstone clarity

    Gemstone clarity is a quality of gemstone relating to the existence and visual appearance of internal characteristics of a diamond called "inclusions", and surface defects called "blemishes".

    Inclusions may be crystals of a foreign material or another gemstone crystal, or structural imperfections such as tiny cracks that can appear whitish or cloudy. The number, size, color, relative location, orientation, and visibility of inclusions can all affect the relative clarity of a gemstone. A clarity grade is assigned based on the overall appearance of the stone under 10x magnification.

    GIA specify gemstone in 3 Type. In each type, gemstones list is different. So gemstone's quality maybe same but the gem's inclusion maybe different. So you can check at the chart below.

    Type 1 - gemstone

    Type 1 - gemstones

    Type 1 - clarity

    Beryl
    Aquamarine
    Green 
    Morganite 
    Yellow

    Chrysoberyl
    Green 
    Yellow

    Quartz
    Smokey

    Spodumene
    Kunzite
    Green

    Topaz
    Blue 
    Yellow 
    Orange 
    Pink 
    Red

    Tourmaline
    Green

    Zircon
    Blue

    Zoisite
    Tanzanite

    VVS - Very, Very Slightly Included (the best) Minute inclusions that are difficult to see using 10X, and are not visible at all to the naked eye.

    VS - Very Slightly Included Minor inclusions that are easier to see using 10X, but still not visible to the naked eye.

    SI1 - Slightly Included I The inclusions are easily seen using 10X, and are noticeable with the naked eye.

    SI2 - Slightly Included 2 The inclusions are more easily seen using 10X, and are quite visible with the naked eye.

    I1 - Included 1 The inclusions are very obvious and they have a moderate negative effect on the over-all appearance or durability of the gemstone.

    I2 - Included 2 The inclusions are very obvious and they have a severe negative effect on the over-all appearance or durability of the gemstone.

    I3 - Included 3 The inclusions are very obvious and they have a severe negative effect on both the over-all appearance and durability of the gemstone.

    Type 2 - gemstone

    Type 2 - gemstones

    Type 2 - clarity

    Andalusite All 

    Chrysoberyl

    Alexandrite

    Corundum
    All colors (i.e.
    Sapphire and Ruby)

    Garnet
    All species and colors 

    Iolite - All

    Peridot - All 

    Quartz
    Amethyst
    Citrine
    Ametrine

    Spinel - All 

    Tourmaline
    Blue 
    Orange 
    Yellow 
    Multi-colored (except watermelon color) 

    Zircon
    Green 
    Orange 
    Red Yellow

    VVS - Very, Very Slightly Included (the best) Minor inclusions that are somewhat easy to see using 10X, but still not visible to the naked eye.

    VS - Very Slightly Included Noticeable inclusions that are easier to see using 10X, and may be slightly visible to the naked eye.

    SI1 - Slightly Included I The inclusions are easily seen using 10X and are large or numerous, and are noticeable with the naked eye.

    SI2 - Slightly Included 2 The inclusions are easily seen using 10X and are large or numerous, and are very noticeable with the naked eye.

    I1 - Included 1 The inclusions are very obvious and they have a moderate negative effect on the over-all appearance or durability of the gemstone.

    I2 - Included 2 The inclusions are very obvious and they have a severe negative effect on the over-all appearance or durability of the gemstone.

    I3 - Included 3 The inclusions are very obvious and they have a sever negative effect on both the over-all appearance and durability of the gemstone.



    Type 1 - gemstone

    Type 1 - gemstones

    Type 1 - clarity

    Beryl
    Emerald

    Tourmaline
    Red 
    Pink 
    Watermelon (green transitioning to pink or red)

    VVS - Very, Very Slightly Included (the best) Noticeable inclusions that are easy to see using 10X, but usually not visible to the naked eye.

    VS - Very Slightly Included Obvious inclusions that are easy to see using 10X, and usually visible to the naked eye. SI1 - Slightly Included I The inclusions are large and numerous using 10X, and prominent with the naked eye.

    SI2 - Slightly Included 2 The inclusions are large and numerous using 10X, and very prominent with the naked eye. I1 - Included 1 The inclusions are very obvious and they have a moderate negative effect on the over-all appearance or durability of the gemstone.

    I2 - Included 2 The inclusions are very obvious and they have a severe negative effect on the over-all appearance or durability of the gemstone.

    I3 - Included 3 The inclusions are very obvious and they have a sever negative effect on both the over-all appearance and durability of the gemstone.

    For this grading, you will know some stone's kind in several type grading. So it is mean, different colors in same gemstone family is not same value amount.  Learn all about gemstones properties like Color, Hue, Tone, Intensity as it will help in identifying genuine gemstone from fake stones, evaluating gemstone quality and source of origin.

    GIA color grading

    GIA color grading is separated to be 3 types. The first one is intensity, or saturation. The second is hue, or color. And the last is tone, or lightness/ darkness. You can see the picture below for comparing the gem's colors.

    1) Hue

    The hue is the actual color of gemstones ex. red, yellow, green and blue. You can see the chart below.

    The GIA hue chart

    2) Intensity

    The gem's intensity, GIA grading in 6 level of saturation ranging by the grey color saturated of gem color. Please see the chart below.

    GIA intensity grading

    3) Tone

    To describe the darkness or lightness of a colored stone, the GIA system has 9 levels of tone ranging from "very very light" to "very very dark." Please see at the chart below.

    GIA's tone chart

    With the exception of hue, each of these parameters by themselves are relatively meaningless and they must be used in conjunction to tell the full story of a gem's color quality. Taken together, these three parameters will provide a simple numeric code that can quickly and accurately quantify gemstone color.

    GIA blue sapphire's color grading

    Example, if you think about "cornflower" color and "royal blue" color of blue sapphire, you can specify the color clearly with other when use the GIA color grading chart.

    Gemstone Inclusions

    The next step is to study any inclusions that may be present. If any doubt exists as to whether they are indicative of natural or manmade origin, check the appropriate assignments in the colored gemstone assignments. Inclusions characteristic of synthetic and other manmade stones are to be found also in the supplement with this course. The subject of the use of characteristic inclusions for identification is covered in detail in the assignment following the next work project. At this point, it is important to examine the pattern of inclusions under low power. Often, inclusions that appear to be unrelated individual entities will be seen to form a very revealing pattern when the stone is examined in this manner. For example, in ruby, sapphire and emerald, a number of inclusions or lines that together present a hexagonal aspect may assist materially in identification. The pattern of rutile needles oriented in three directions at 60° to one another in the same plane is a very strong indication of corundum, or at least of the hexagonal crystal system.

    Types of Inclusions

    Crystals: are solid mineral inclusions of various shapes and sizes. Genuine Ruby and Sapphire will have crystal inclusions like pyrite, garnet, zircon, calcite and spinel. Minute crystals are called pinpoints or grains.

    Negative Crystals: are hollow spaces inside a stone that have the shape of a crystal.

    Silk: in ruby and sappgire consists of very fine fibers of rutile (titanium oxide) or other minerals. These fibers or rows intersect and rsemble silk. Well formed silk is a good indication that stone has not been heat treated.

    Needles: are long, thin inclusions that are either solid crystals or tubes filled with gas or liquid and are called growth tubes.

    Fluid Inclusions: are hollow spaces filled with fluid. They occur in random shapes and are sometimes dense creating a milky look. Fluid inclusions are of three types: single phase inclusions with only fluids; two phase inclusions with liquid and gas and three phase with a liquid, a gas and a solid. Type of inclusions can also help in identifying source of the gemstone.

    Cracks (Fractures or Fissures); of various sizes are commonly seen in ruby and sapphire. Cracks are also referred to as feathers.

    Parting: refers to breakage along a plane of weekness. In ruby and sapphire parting planes are thin seams of boehmite.

    Twinning: occurs when two or more crystals of the same mineral are united and are generally seen as straight lines.

    Halos: are circular fractures around a crystal and during heating the crystal can expand.

    Fingerprints: are very common in ruby and sapphire and are healed cracks and look like human fingerprints.

    Saturn: like inclusions have a central core with the shape of flattned sphere surrounded by a planar circular. The core be solid, hollow or fluid and gas. The surface of the core is smooth and metallic or granular like a snowball. Saturn like inclusions are found in rubies from Thailand and Cambodia and are a good indication that helps gemologists determine country of origin.

    Growth or Color Zoning: are referred to uneven distribution of color and if color zones look like bands they are called growth or color bands.

    Cavities: are holes into a stone from the surface and can be caused during stone cutting process.

    Chips: are broken off pieces of stone along the girdle or at the culet.

    Now that you are familiar with gemstones properties like Refractive Index, Double Refraction, Birefringence, Specific Gravity, Inclusions it will help in identifying genuine gemstone from fake stones, evaluating gemstone quality and source of origin. The tables below show typical inclusions found in genuine gemstones and fake stones as well as have unique Refractive Index, Double Refraction, Birefringence and other properties. Every gemstone has its own unique identity and genuine gemstone identification is a process that involves identifying gemstones structure and chemical properties. Genuine gemstone identification requires gemological knowlege, gemology tools and a well trained experience eye. There are many ways to identify a real gem from a fake one as well as how to evaluate gemstones quality and its origin.

    Characterstics of Genuine Rubies, Sapphires and Emeralds:

    Parameters Ruby Sapphire Emerald
    Chemical Composition Al2O3 Al2O3 Be3Al2(SiO3)6
    Moh's Hardnes 9 9 7.5 to 8.0
    Specific Gravity 4.0 4.0 2.72
    Toughness Excellent Excellent Poor to Good
    Clevage None None Indistinct
    Parting Rhomoohedral Rhomoohedral --
    Fracture Uneven Uneven Uneven
    Steak White or Colorless White or Colorless White
    Crystal Symbol Hexagonal Hexagonal Hexagonal
    Optic Character Doubly Refractive Doubly Refractive Doubly Refractive
    Refractive Index 1.765 1.765 1.578
    Birefringence .008 to .010 .008 to .010 .005 - .009
    Dispersion 0.018 .018 0.014
    Luster Subadamantine to Vitreous Subadamantine to Vitreous Vitreous
    Phenomena Asterism (6 to 12 rays), Color Change from Blue to Purple Asterism (6 to 12 rays), Color Change from Blue to Purple --
    Dichroism Purplish Red Blue Sapphire:Violetish & Greenish BlueYellow Sapphire:Yellow or Greenish YellowOrange Sapphire:Orange or Brownish OrangeGreen Sapphire:Green & Yellow GreenPurple Sapphire:Violet & Orange Yellowish Green
    Chelsea Filter Strong Red Blackish Pink to Red
    Absorption Spectra Fluoroscent at 694 & 693 nm Three Bands at 451.5, 460 and 470 nm Distinct Lines at 683 and 680.5 nm
    Color Reason Chromium (Iron & Titanium Present Sometimes) Blue: Iron & TitaniumYellow: Iron and/or Color CentersOrange: Iron and/or Color CentersGreen: Iron or Iron & TitaniumPurple: Chromium, Iron and Titanium Chromium, Vanadium and/or Iron.
    UV Fluoroscence Strong to Weak Red or Orange Red Blue: Strong Red to Orange to inert.Yellow: Moderate Orange-Red to inert.Orange: InertGreen: InertPurple: Stong Orange Red Usually Inert
    Heat Reaction Turns Green but turns back to Red on cooling.   Additional Fracturing
    Chemical Reaction Highly Resistant   Resistant except Hydroflouric Acid
    Light Stability Stable   Stable

    Characterstics of Facetted Rubies, Sapphires and Emeralds from Finest Mines:

      Fluoroscence Inclusions
    Kashmir Sapphire Orangy Fluoroscence Sharp, Wide Spaced, Straight Zones, Powdry Texture, Glowy Quality
    Burma Ruby -- Small Nests like concentrations of tiny rutile needles, color swirls, streamers, calcite and domomite inclusions, graining
    Buma Sapphire -- Dense Clouds of rutike silk similar to ruby, silk shorter and more densely packed, fingerprints common, even color and no banding
    Ceylon Ruby -- Very Long, fine rutile needles that traverse the whole stne, fingerprints, feathers, negative crystals, uneven coloring, other crystals such as calcite, garnet, pyrite, tourmaline, spinel and apitite.
    Ceylon Sapphire A uniform orange or red fluoroscence Very Long, fine rutile needles that traverse the whole stne, fingerprints, feathers, negative crystals, uneven coloring, other crystals such as calcite, garnet, pyrite, tourmaline, spinel and apitite.
    Thai Ruby   Saturn inclusions which are solid crystals surrounded by fingerprints, no rutile silk, fingerprints wispy like flux inclusions seen in synthetic corrundum, crystals such as pyrrhotite, apitite, garnet, color zoning rare, twinning common, needles which intersect in 3 directions
    Thai Sapphire Inert Slightly smilky, no rutile silk, strong and uneven color zoning, white needles, fingerprints, crytals such as feldspar and hornblende
    Cambodian Sapphire Inert White boehmoite neddles but no rutile silk, fingerprints and feathers, inclusions with crstal and halo,
    Australian Sapphire Inert Crystals like Cambodian Sapphires, fingerprints and feathers, zoning and color banding,
    Tanzanian Sapphire   Twinning planes and boehmite , tiny thin plats of films
    Brazalian Emerald   Biotite, dolomite, pyrite crystals, chromite grains, growth tubes
    Colombian Emerald   Three phase inclusions, jagged borders, gas bubble, halite crystals, albite feldspar, pyrite, calcite
    Mozambique Emerald   Two phase inclusions, biotite crystals
    Indian Emerald   Two phase inclusions
    Pakistan Emerald   Growth tubes, fluid inclusions, chromite, dolomite
    Tanzanian Emerald   Biotite mica, garnets
    South African Emerald   Biotite flakes, molybdenite
    Zambian Emerald   Limonite filled tubes, mucovite mica, tourmaline crystals, hematite platelets, rutile prisms

    Characterstics of Synthetic Rubies and Sapphires:

    Synthetic Ruby & Sapphire Spectra Fluoroscence Chelsea Filter Inclusions
    Verneuil Sapphire: No iron lines

    Ruby: Strong Red than both natural and other synthetic rubies

    Sapphire:Inert, weak to strong red or orange red

    Green Sapphire: Red Curved growth lines, tiny and large spherical gas bubbles, whitish particles of Al203, small dark red crystals
    Inamori  

    Ruby: stronger red than natural

    Sapphire Orange: Strong orange red

      Whitish Clouds, gas bubbles, faint growth curved lines, rain like particles
    Seiko       Clouds of gas bubbles, swirled and curving growth or color zoning more like foogy Kashmir Sapphire
    Chatham Sapphire: A Diffuse Band at 451.5 nm     Platinum plates and needles, white or yellowish flux, seed and accidental crystals
    Ramaura   small chalky yellow areas, dull, chalky red to orange   Flux inclusions

    Characterstics of Synthetic Emeralds:

    Synthetic Emerald Refractive Index Birefingence Inclusions
    Kimberly 1.570 0.004 - 0.005 Nail head spiculle inclusion with gas and liquid phases, growth features, gold and phenakite crystals, healing fussures
    Chatham 1.560 0.003 - 0.004 Flux fingerprints and veils of whitish, orangy, or brownish flux, platinum, phenakite crystals, parrallel growth planes, two phase gas and liquid inclusions
    Gilson 1.565 0.005 Flux fingerprints and veils of whitish, orangy, or brownish flux, platinum, phenakite crystals, parrallel growth planes, two phase gas and liquid inclusions
    Linde 1.560 0.003  
    Russian 1.560 0.004 Flux fingerprints and veils of whitish, orangy, or brownish flux, platinum, phenakite crystals, parrallel growth planes, two phase gas and liquid inclusions

    Characterstics of High-Quality Sapphires:

      Kashmir Sapphire Burma Sapphire Ceylon Sapphire Thai Sapphire
    Hue violetish blue to blue violetish blue to blue violetish blue to blue, masked by gray

    violetish blue to greenish blue, masked by gray

    Tone medium to medium dark medium dark to very light medium dark to very light very dark to medium dark
    Gray Color Masking minimum minimum    
    Appearance powdery, velvety      
    Color looks good in any kind of light but bluest under fluoroscent lighting, color highly saturated due to tone and color purity Color more evenly distributed than Kashmir and Ceylon Sapphires, color highly saturated due to tone, color purity and uniform color unevenly distributed, the more even the color the better the stone, more brilliance due to lighter color, less saturated than Burma & Kashmir Sapphires due to light tones, gray color masking and uneven color lot of black extinctions, more blue less black is more valuable, less saturated than other sapphires

    Characterstics of High-Quality Rubies:

      Burma Ruby Ceylon Ruby Thai Ruby
    Hue orangy red to purplish red to pinkish red orangy red to red

    purplish red to orangy red

    Tone medium to medium dark medium to very light medium dark to very dark
    Gray or Brown Color Masking no   often masked by gray, brown or black
    Fluoroscence Good red Good Red Very Little
           
    Appearance Black extinctions are minimum, stones look red throughout Few Dark Extinctions Area due to red fluoroscence and lighter color Lot of Black Extinction Areas
    Color Color is highly saturated due to tone, purity of color and fluoroscence, pink overtones, color zoning unevenly distributed More red and less black the better the stone

    Characterstics of High-Quality Emeralds:

      Muzo Mine, Columbia Zambian Sandawana, Zambia
    Hue bluish green strongly blue

    yellowish green

    Tone medium to medium dark medium to medium dark medium dark to very dark
    Gray or Brown Color Masking no no no
    Color Grass Green homogenous color yellowish green

    Approximate Weight of Cut Round Emeralds, Rubies & Sapphires

    Size Emerald Ruby & Sapphire
    2 mm 0.04 0.04
    3 mm 0.09 - 0.12 0.11 - 0.14
    4 mm 0.20 - 0.27 0.26 - 0.34
    5 mm 0.40 - 0.48 0.52 - 0.63
    6 mm 0.70 - 0.81 0.80 - 1.08
    7 mm 1.15 - 1.28 1.42 - 1.70

    GIA Ruby Emerald Sapphire Clarity Grades

    VVS Very Very Slightly Included - usually invisble to naked eye
    VS Very Slighty Included, sometimes visible to eyes
    SI1-2 Obvious Inclusions, visble to eyes
    I1 Moderate Effect on appearance and durability
    I2 Severe Effect on appearance or durability
    I3 Severe Effect on appearance and durability

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