Optical properties
Color: Colorless, light to dark purple, light yellow, medium to dark yellow, light to dark brown, brown, green to yellow-green, light to medium pink.
Amethyst: Light to dark purple.
Citrine: light yellow, medium to dark yellow.
Sapphire: light blue, dark blue. Almost all blue crystals are synthetic.
Smoky quartz: light to dark brown, brown. Since Al3+ replaces Si4+ in the composition, [AlO4]4-color center is produced after irradiation.
Green Crystal: Green to yellow-green. Color formation is related to Fe2+, and naturally occurring green crystals are almost non-existent on the market, usually an intermediate product formed by amethyst in the process of heating into citrine.
Hibiscus Stone: Light to medium pink with a lighter hue. It is usually pink due to the presence of trace amounts of titanium (Ti). It can have a transmissive starlight effect.
Crystalline: colorless, light yellow, light brown, etc., can be golden, brownish and other colors because of the presence of rutile, and the gray-black color of tourmaline; It contains actinolite and is grayish-green.
Luster: Vitreous luster. The fracture is greasy and shiny. Luster, an optical property of light reflected on the surface of a gemstone. Observe the luster of the crystal, you can hold it in your hand, and see the reflection of the surface with the light cast by the light or the window, the brightness of the transparent crystal is related to the strength of the luster.
Transparency: The transparency of a crystal is related to the quality and quantity of light that passes through it. When the light is transparent over crystal fragments or flakes with a thickness of more than 1 cm, the reflected image can be clearly seen. If the base image is not clear enough and only the outline is visible, it is translucent.
Refractive index (RI): 1.544-1.553, barely beyond this range. (The refractive index is the ratio of the incidence angle sine to the refraction angle sine when light penetrates the gemstone crystal from the air and produces a refraction phenomenon.) ）
Double fold rate (DR): 0.009 (maximum), this value is very stable.
Dispersion value: 0.013. Dispersion means that the refractive index of a gemstone varies with the illumination. For example, a diamond refracts 2.405 to red, 2.427 to green, and 2.449 to violet.
Photogenicity: One-axis crystalline positive photogenicity. The one-axis crystal interferogram seen under orthogonal polarization is unique, and its black crosshair arm does not reach the center, forming a hollow pattern, commonly known as bull’s-eye interferogram. The central part is usually pale green or pale pink.
Pleochroism: Colorless crystals do not have pleochroism. Colored crystals have weak to strong pleochroism. It is manifested by different shades of body color.
Mechanical properties
Cleavage: No cleavage. Cleavage refers to the property of a mineral that cracks regularly in a certain direction to form a smooth plane when it is struck. 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 crystals belong to no cleavage.
Fracture: shell-like. A breach is also called a breach. It refers to the irregular fracture of the mineral after it is struck, and the uneven cracking surface is called a fracture. According to the shape of the fracture, it can be divided into shell-like and serrate-like.
Hardness: Mohs hardness 7, which is Mohs hardness, is equivalent to the general hardness of steel files. In 1824, a man named Frisch. Austrian mineralogists from Moss extracted 10 varieties of minerals and measured their relative hardness through scientific experiments, resulting in a crystal hardness of 7 on the Mohs scale. Although the National Bureau of Standards later used and promoted the more scientific Noop hardness tester, jewelers in many countries around the world are still accustomed to the Mohs hardness chart.
Density (specific gravity SG): 2.66 (0.03, 0.02) g/cm3. This means that the weight of a certain volume of crystal is 2.56-2.66 times the weight of the same volume of water. Lumpy variant crystals may be slightly denser.
Piezoelectric: Crystal crystals generate electric charges when they are subjected to pressure; Conversely, when subjected to voltage, the crystal will vibrate at a very high frequency. Crystals have the ability to transfer pressure and charge to each other, which is called piezoelectricity.
Streak color: colorless. The color of the mineral powder is called streaks. It can eliminate false color, weaken other color, and retain self-color, which is one of the more reliable identification characteristics than the color of minerals.
Melting Point: The melting point of crystal is 1713°C. Its fragile properties were discovered during experiments. Crystals are placed on the flames of the flamethrower and roasted, as they are prone to shattering unless they are well protected and cooled slowly. The ancients had already figured out this temperament.
Other properties
(1) Piezoelectric effect: Under the action of mechanical force (pressure or tension), the two ends of a crystal single crystal will produce an electric charge, which has an equal amount of electricity but opposite signs. In industry, colorless, defectless, and non-bicrystalline crystals are often used as piezoelectric quartz sheets.
(2) Thermal conductivity: better than glass, but worse than most minerals, and directional.
(3) Hot melting: the crystal is difficult to melt, and it will only melt when the temperature reaches about 1715 °C, and the melting point can be reduced when there are inclusions.
(4) Boiling point: 2477 °C
(5) Chemical stability: very good, only dissolved in hydrofluoric acid at room temperature, insoluble in other acids and alkalis. It can be dissolved in sodium carbonate solution under high temperature and high pressure conditions.
(6) Solubility: At room temperature and pressure, the crystal is insoluble in water.