crystal

crystal

This data is reviewed by the project of data compilation and application of Science Encyclopedia of science popularization in China.

Rock crystal is a rare mineral, a kind of gem, quartz crystal, which belongs to the quartz group in mineralogy. The main chemical composition is silica, and the chemical formula is SiO < sub > 2.

The crystal is colorless and transparent when it is pure. When it contains trace elements such as Al and Fe, it is pink, purple, yellow and tan. After irradiation, trace elements form different types of color centers and produce different colors, such as purple, yellow, Tan, pink, etc. The inclusions containing associated inclusion minerals are called inclusion crystals, such as hair crystals, green ghost, red rabbit hair, etc., and the inclusions are rutile, tourmaline, actinolite, mica, chlorite, etc.

Interpretation of words

Crystal refers to colorless and transparent silica crystal, which belongs to precious ore. At present, it is juxtaposed with ice colored chalcedony, tourmaline, etc. into the category of colored gemstones, with less output. It was called "Shuiyu" and "Shuijing" in ancient times. He quoted Zizhitongjian, the second year of Tianfu, the emperor of Gaozu in the later Jin Dynasty, as saying, "the master of Fujian made Ziwei palace and decorated it with crystal." In ancient and modern novels, Master Li is satisfied with saving snakes: "the utensils are made of glass, crystal, amber and agate. The music is so ingenious that it is not owned by human beings." Preface to selected poems of Ai Qing: "meditate on the shape of flower dew and love the quality of crystal." "The bird pecks at the ice pool, the jade mirror opens, the wind blows on the eaves, the crystal is broken." Xu Wei of Ming Dynasty wrote a poem about Banyou in the western suburbs: "Han Han contains ice brain, cherry drops crystal." "The cool toad is rising in the high Pavilion, the curtain is rolling, and the wind is reflecting the crystal." Chen Weisong of the Qing Dynasty wrote "Bodhisattva man: the painting album of Qingxi legacy": "you still remember to play hide and seek, the crystal courtyard is cool."

brief introduction

Rockcrystal is a kind of quartz crystal mineral, its main chemical composition is silica, the chemical formula is SiO < sub > 2 < / sub >. Western countries believe that as long as it is transparent, it is crystal, so the word crystal includes colorless and transparent glass (K9, ordinary glass bluish), and also contains natural crystal ore. There are more than ten ancient names of crystal in China, such as Shuijing, shuibi, Shuiyu, Jingshi, etc. The well-developed single crystal is hexagonal cone, so it is usually massive or granular aggregate, generally colorless, gray, milky white, and purple, red, smoke, tea, etc. when containing other mineral elements. when the silica crystal is perfect, it is crystal; when the crystal is not perfect, it is quartz: after the silica gel is dehydrated, it is agate; after the silica gel containing water solidifies, it becomes opal; when the silica crystal is less than a few microns, it forms chalcedony, flint and secondary quartzite. chemical composition: silica, containing si-46.7% and o-53.3%. Because it contains different trace elements or color centers, it presents a variety of colors. mineral composition: goethite, hematite, rutile, magnetite, tourmaline, garnet, mica, chlorite, etc. form inclusion crystals, such as hair crystal, titanium crystal, green ghost, etc. the hair crystal contains the inclusion formation of hair like acicular minerals visible to the naked eye. Those with manganese and iron are called Amethyst; those with iron (; golden yellow or lemon color) are called Topaz; those with manganese and titanium in rose color are called Rosary quartz, i.e. powder crystal; those with smoke color are called smoke crystal; those with brown color are called tea crystal; those with black transparency are called ink crystal. crystal habit: the crystal with perfect crystal belongs to the cubic crystal system. It is often hexagonal crystal, with horizontal lines on the cylinder surface. The cylinder is pointed at one end or two ends. Many long cylinders are connected together, which is called crystal cluster. It is beautiful and spectacular, and its shape can be described as various. In addition to the common long columnar shape, there are sword like shapes, some plate-like, some short columnar, some biconical. Some are as small as fingers, some as big as boulders, some are less than half Liang, some weigh more than 300 kg. Chairman Mao Zedong's crystal coffin finally selected high-quality natural white crystal from Donghai County 105 mine as raw material. At present, the largest crystal is also from Donghai County, Lianyungang.

nature

optical properties

Color:

Colorless, light to dark purple, light yellow, medium to dark yellow, light to dark brown, brown, green to yellowish green, light to medium pink. amethyst: light to dark purple. Topaz: light yellow, medium to dark yellow. Blue Crystal: light blue, dark blue. Almost all blue crystals are synthetic. smoke crystal: light to dark brown, brown. Because Al3 + replaces si4 +, 4-color centers are formed after irradiation. green crystal: green to yellowish green. The color formation is related to Fe2 +. There is almost no natural green crystal in the market, which is usually an intermediate product formed in the process of heating Amethyst into topaz. Hibiscus stone: light to medium pink, light tone. It is usually pink because it contains trace titanium (TI). It can have the effect of transmitting starlight. crystallization: colorless, light yellow, light brown, etc., which can be caused by rutile, tourmaline and actinolite.

Gloss:

Glass luster. The fracture surface is glossy with grease. Luster refers to the optical property of a gem surface reflecting light. To observe the luster of crystal, you can hold it in your hand and see the surface reflection with the light or the light from the window. The brightness of transparent crystal is related to the luster.

Transparency:

Crystal transparency is related to the quality and quantity of light passing through it. When the light is transparent through crystal fragments or flakes with a thickness of more than 1cm, the image can be clearly seen. If the background image is not clear enough, only the outline can be seen, it is translucent.

Refractive index

(RI): 1.544-1.553. (refractive index refers to the ratio of the sine of the incident angle to the sine of the refraction angle when light penetrates into the gem crystal from the air and refracts.)

double

Discount rate

(DR): 0.009 (maximum), which is very stable.

Dispersion value

：0.013。 Dispersion means that the refractive index of a gem varies with the illumination. For example, the refraction of diamond to red light is 2.405; to green light is 2.427; to purple light is 2.449.

Light property:

The optical properties of uniaxial crystal are positive. The uniaxial crystal interferogram under orthogonal polarized light is unique. Its black cross arm does not reach the center, forming a hollow pattern, commonly known as the bull's eye interferogram. The central part is usually light green or pink.

Polychromism:

Colorless crystals are not polychromatic. Colored crystal has weak to strong polychromism, which is shown by different shades of body color.

mechanical property

cleavage

No cleavage. Cleavage refers to the property that minerals are cracked regularly along a certain direction to form a smooth plane when they are hit. According to the degree of cleavage, it can be divided into five categories: extremely complete cleavage, complete cleavage, medium cleavage, incomplete cleavage and non cleavage. Crystal belongs to non cleavage.

fracture

Conchoidal. Fracture is also called breach. It refers to the irregular fracture of minerals after being hit. The uneven fracture surface is called fracture. According to the shape of fracture, it can be divided into shell shape and serrated shape.

hardness

The hardness is 7, which is equivalent to the hardness of steel file. In 1824, an Austrian mineralogist named Frisch moss extracted 10 varieties from many minerals and measured their relative hardness through scientific experiments. Thus, the crystal hardness was 7. Although more scientific Knoop hardness tester was used and promoted by the National Bureau of standards of the United States, jewellers in many countries in the world are still used to Morse hardness tester.

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 that of the same volume of water. The density of massive variant crystal may be slightly higher.

Piezoelectricity

: crystal will produce electric charge when it is under pressure; on the contrary, crystal will produce high frequency vibration when it is under voltage. Crystal has the ability to transfer pressure and charge, which is called piezoelectricity.

Stripe color:

Colorless. The color of mineral powder is called streak. It can eliminate false color, weaken other color and retain self color. It is one of the more reliable identification characteristics than mineral color.

melting point

The melting point of the crystal is 1713 ℃. It is easy to break when heated, which was found in the experiment. Put the crystal in the flame of the flame burner. Unless it is well protected and cooled slowly, the crystal is easy to break. The ancients have understood this temperament.

Other properties

① Piezoelectric effect: under the action of mechanical force (pressure or tension), the two ends of a single crystal will produce electric charges. The electric charges are equal, but the sign is opposite. In industry, crystal without color, defect and double crystal is often used as piezoelectric quartz chip.
(2) thermal conductivity: better than glass, but worse than most minerals, and directional.
(3) hot melt: the crystal is difficult to melt, and only melts when the temperature reaches about 1715 ℃. When there are inclusions, the melting point can be reduced.
(4) boiling point: 2477 ℃ < br > ⑤ chemical stability: very good, only soluble in hydrofluoric acid at room temperature, not soluble in other acids and bases. It can be dissolved in sodium carbonate solution under high temperature and high pressure.
Solubility: under normal temperature and pressure, the crystal is insoluble in water.

grow

Most of them are under the ground and in caves, and they need to be rich

Chinese PinYin : Shui Jing