Depending on the color and special optical effects, the crystals can be divided into different gemstone varieties.
(1) Colorless crystal: colorless and transparent, the composition is pure, transparent, no inclusions and no cracks of large crystals are difficult to see. It is generally used as a carving material, and is best known for making crystal balls, mainly as a household ornament. The world’s largest and most transparent and flawless crystal ball, with a diameter of 21 cm, is now in the collection of the Smithsonian Museum in Washington, D.C., USA.
(2) Amethyst: generally light in tone, uneven color distribution. Amethyst also includes purplish-red and crimson-colored transparent water crystals. It is the most expensive of the crystals, and it is the February birthstone, and it often has a more obvious dichroism.
(3) Citrine: because of the trace amount of Fe and yellow-orange-red, brownish-yellow, mostly transparent columnar crystals, the yellow-brown crystals that are often seen by amethyst heat treatment and discoloration on the market at present.
(4) Smoky quartz, citrine and ink quartz: smoky yellow is called smoky quartz, dark brown is called citrine, and black is called motif. Some people believe that these crystals are mainly mixed with a different number of extremely fine particles and evenly distributed carbon elements, others believe that these crystals contain tiny particles (such as a large number of gases or free silicon atoms) and are formed, and others believe that the crystals contain trace amounts of A1, A13+ ions instead of Si+ ions, and are caused by the formation of hole color centers after being ejected.
(5)rutilated quartz Hair crystal: A crystal variety containing elongated rutile like hair, black or colored tourmaline, green hornblende, white asbestos, actinolite that sparkles like silk, etc. This type of inclusion makes the crystal very beautiful, and this water crystal, which does not need to be finely processed, can be used as an ornament with a little contemplation.
(6) Hydrochic crystal: The crystal contains inclusions of natural mineralized aqueous solution visible to the naked eye, which is called a rare treasure because it is very rare.
(7) Rose crystal: containing Mn and Ti and pink block crystal, in most cases the crystal shape is not good, in some crystals, because of the microscopic needle-like rutile, they are distributed along the vertical C-axis in three directions at an angle of 120 ° to each other, after pondering into an arc, there is a six-ray starlight, also known as “starlight rose crystal”.
(8) Quartz cat‘s eye: When the crystal contains a large number of fibrous inclusions arranged in parallel (such as asbestos fibers), its curved gemstone surface can show a cat’s eye effect, which is called quartz cat’s eye.
(9) Star crystal: when the crystal contains more than two groups of needle-like, fibrous inclusions arranged in a directional manner, the surface of the curved gem can show the starlight effect, generally six-ray starlight, but also four-ray starlight.