2. Meteorite diamond is a newly discovered substance, and its formation mechanism is unknown. At present, there are only two meteorite diamonds in the world, and China has one. Its main component is carbon, accounting for 90%, and 10% is zinc, magnesium and other elements.
3. Hexagonal crystal system, which has a sixth symmetry axis or a sixth anti-rotation axis, and this axis is the vertical crystal axis C axis of the crystal. The positive ends of the other three horizontal crystal axes form an included angle of 1200. Axis angle α = β = 900, γ =1200, and axis unit a = b ≠ C. Representative minerals: emerald and beryl containing chromium. The chemical composition is Be3Al2[Si6O 18]. Hexagonal crystal system, the crystal is hexagonal column with longitudinal stripes. Glass luster, hardness 7.5. Stable performance, not easy to be corroded. It is a precious gem, and its transparent green color is the main identification feature. The lightness and brightness of its color mainly depend on the content of chromium oxide and iron oxide. The more iron oxide, the darker the color and the lower the quality.