1, single crystal gem
Single crystal mineral gemstones are usually transparent and glassy. Such as diamond, corundum, beryl, chrysoberyl, tourmaline, quartzite, feldspar, topaz, spinel, zircon, garnet, olivine, tanzanite, spodumene, prehnite, diopside, cordierite and sillimanite.
2. Polycrystalline gemstones
Polycrystalline mineral gem is generally jade, which is a collection of various crystals. For example, jadeite, nephrite, serpentine, dushan jade, lantian jade, turquoise, lapis lazuli, malachite, sugleite, xonotlite, Yingshi, chalcedony, Shi Yuhua, Mubian, Miyu, Huang Longyu, Beijing white jade, white marble, jade, opal shoushan stone, bloodstone and so on.
3. Organic gemstones
Organic gemstones are directly related to natural organic substances, which are partially or completely composed of organic substances and can be used as materials for ornaments. For example, pearls are formed in shellfish or mussels, and contain a lot of inorganic components and a certain amount of organic components, so they are organic gems. Coral fossils, pearls, shellfish fossils, amber fossils, mammoth ivory, tortoise shells, bones, horns, wood fossils, etc.
Formation principle of natural gemstones
1, magmatism
Most of the magma comes from tens of kilometers underground and is formed by high temperature melting. Usually, these high-temperature slurries rush from underground to the surface along cracks, and become hard stones after cooling. Therefore, magmatism includes magmatic intrusion, volcanic eruption and post-magmatic hydrothermal process.
2. Settlement
In the late Mesoproterozoic, the southern margin of Tarim ancient land, where the northern margin of Kunlun Mountain is located today, was once a shallow sea zone, where there were a lot of carbonate deposits, among which magnesium-bearing dolomite was one of the main sources of jade. Therefore, sedimentation includes biological debris accumulation, debris accumulation, chemical precipitation, supergene leaching and so on.
3. Deformation
During the Sinian period at the end of Proterozoic, the Tarim movement caused strong fold and fault activities in the whole region, and finally formed the Tarim continent. In extensive regional metamorphism, dolomite is transformed into dolomite marble. Therefore, metamorphism is the main cause of jadeite, including regional metamorphism, contact metasomatism metamorphism, hydrothermal alteration and so on.