Gems, minerals and precious stones all come in crystalline forms that offer visual appeal. When choosing such stones for personal use, your own taste is usually the guiding factor. The classifications of the rocks have to do with the chemical components and qualities of the various minerals. Visit any gem or rock shop and you will find thousands of types, sizes, colours and styles of crystal, each with its own attributes, according to collectors, historians and metaphysical practitioners. Choose the types that appeal to do you, directly.
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Quartz comes in many kinds of crystal. It can be 100 per cent clear, or have tints, cloudiness, mixes of other minerals and rutiles. Clear quartz, smoky quartz and rose quartz are common. The golden citrine rocks can have tiny or large crystals. Amethyst stones are usually purple, and are often found inside geodes. These rocks look fairly ordinary and dull on the outside, but once cut open, reveal beautiful crystals inside.
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Halides and Silicates
Cryolite, fluorite, halite, sylvine and calomel are just a few of dozens in the halides mineral class. The silicates class is a large group of minerals with complicated structures. Humite, olivine, topaz, datolite, kyanite, staurolite and the garnet family appear in the silicates.
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Sulphates and Sulfides
Common to the sulphates group are gypsum, baryte and anhydrite. The beautiful light blue celestite is a heavenly stone to discover. Also included in the sulates are caledonite, uranopilite, polyhalite and the keiserites. Some of these stones have fluorescent qualities, making them glow in the dark. The sulphides are a large group with several subgroups. Molybdenite, galena, the scarlet coloured cinnabar, kermesite, and pyrite -- or "fool's gold" -- fall into the sulphides.
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Carbonates and Phosphates
The calcite and aragonite groups in the carbonate class present beautiful sparkling crystals, among them, the brilliant pinks of rhodochrosite. Malachite is a green rock with many crystal variations. Others in this group are pirssonite, trona, stichtite and azurite. The phosphates class is composed of a large number of minerals, the most common of which fall into the apatite group. Beryllonite, vauxite, dufrenite and wolfeite are but a sampling of this extensive class.