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Opal:
Opal is a very unregular mineral. The chemical formula is SiO2 *
nH2O, but the structure is far from the struture of Rock crystals and
Amethysts. Opal has got much colors which change with the beam of
light angles and so opal gleams. The reason for this effect is that
opals contains water. When opal desiccates then this effect is away.
Then it is good to put the opal for some time into water and then the
effect returns. In antiquity this stone was very expensive and people
thought that he has got positive effects. We can find much Opal in
Australia and in Mexico. Until today Opal is used for jewels and he
is expensive. Mostly Opal is slided roundly. In former times in Rome
opal was very important.
Data about
the Opal
Chemical
formula SiO2 * nH2O
Mineral class oxides
Crystal system amorph
Hardness 5 to 6.5
Density 1.9
g/cm3 to 2.5 g/cm3
Color many colors
Line color white
Gloss fat gloss
Break shell
Fissileness none |
