Physical properties of crystal gemstones

Crystal chemical composition

Crystal and ordinary sand are a substance of "the same mother." When the crystallization of silica is perfect, it is crystal; after silica gelation and dehydration, it is agate; the colloid of water containing silica becomes solid as an opal; when the crystallite of silica is less than a few microns, it is composed of chalcedony, vermiculite, and secondary. Quartzite.

Pure, colorless, transparent crystal is a variant of quartz. The chemical composition contains Si-46.7%, O-53.3%. Multiple colors are present due to the inclusion of different incorporations or mechanical incorporation. Purple and green are colored by iron (Fe2+) ions, purple can also be caused by titanium (Ti4+), and other colors are colored by color centers. In the crystal, there are inclusions such as sand-like, fragmented goethite, hematite, rutile, magnetite, garnet, chlorite, etc.; in the crystal, it contains a package of hair-like needle-like minerals visible to the naked eye. Body formation. Those containing manganese and iron are called amethyst; those with iron (gold or yellow) are called citrine; those with manganese and titanium are called rose quartz, which is called pink crystal; those with smoke are called smoke crystal; those of brown are called brown crystal. Tea crystal; black transparent is called ink crystal.

The physical and chemical properties of crystal

1. Hardness: It is a Mohs hardness of 7, which is equivalent to a steel crucible.

2, cleavage: no. The so-called cleavage refers to the fact that when a mineral is struck, it is regularly cracked in a certain direction to form a smooth plane. According to the degree of cleavage, it can be divided into five categories: extremely complete cleavage, complete cleavage, medium cleavage, incomplete cleavage and no cleavage, and crystal belongs to no cleavage.

3, fracture: shell-like. The fracture is also called a breach. It refers to the irregular cracking of the mineral after being hit, and the rugged surface is called the fracture. According to the shape of the fracture, it can be divided into: shell shape and jagged shape.

4. Specific gravity: The specific gravity of the crystal is 2.56-2.66 g/cm 3 . The weight of the same volume of crystal is 2.56-2.66 times the weight of the same volume of water, and the crystal density of the block variant may be slightly higher.

5, streaks: colorless. The color of mineral powder is called streaks. It can eliminate false colors, weaken the color, and retain the self-color, which is one of the more reliable identification features than the color of minerals.

6. Transparency: transparent and translucent. The degree of light transmission of minerals is called transparency. The crystal's transparent standard is that when the light passes through crystal fragments or sheets with a thickness of 1 cm or more, the reflected image can be clearly seen. If the bottom image is not clear enough, only the outline, that is translucent.

7, gloss: glass luster. Gloss is the ability of a mineral surface to reflect light. Observe the luster of the crystal, hold it with your hand, and see the surface reflection by the light projected from the light or window. The brightness of the transparent crystal is related to the gloss.

8. Refractive index: The refractive index of crystal is 1.544-1.553, which hardly exceeds this range. The refractive index refers to the ratio of the sine of the incident angle to the sine of the angle of refraction when light is transmitted from the air into the gemstone crystal.

9, the melting point of crystal: the melting point of crystal is 1713 ° C.