Crystal is a very popular gem. In ancient times, it was called water essence, that is, water essence. In addition, it is also called Shuiyu, Baifu, Yujing, Millennium Ice, Bodhisattva Stone, Flash Stone and so on. Aristotle, a famous philosopher in ancient Greece, also believed that crystals evolved from ice. In fact, crystal is a crystal of silicon dioxide, which has no internal connection with water or ice. Usually colorless and transparent, but it can have different colors when it contains iron elements, such as purple, yellow, smoky gray and so on. When the crystal contains fibers or needle-like minerals arranged in a certain direction, it can be processed into crystal cat's eye or starlight crystal or hair products, and if it contains water inclusions, it may become crystal-filled.

China and Jiangsu Donghai crystal production accounts for half of the country, and is known as the "hometown of crystals". For a long time, crystal has been regarded as a sacred object because of its crystal clear, moist and pure, and it is considered to be a symbol of good luck, which can "resist evil spirits and repel ghosts and gods". Crystal ornaments are cool and gorgeous. Wear the Great Wall of Wan Li in summer to add coolness and relieve the stimulation of summer heat. In the northwest of China, people suffering from ocular fire (an eye disease) think that wearing crystal glasses can dispel the fire in their eyes, thus eliminating eye diseases. The whiteness of the crystal also makes people believe that there are gods hidden in it. Making it into a ball and staring at it can predict the future, so the Japanese are always happy to display crystal balls at home.

Among the varieties of crystal, amethyst is the most precious. In addition to its elegant color, our ancestors have always believed that amethyst can promote mutual understanding and bless everything. At present, bishops of the Roman Cathedral often wear amethyst rings, and wine is served in goblets made of crystal at ceremonies. In addition, the crystal contains a variety of elements beneficial to the human body and is not radioactive. All these make crystal and its products attract people's attention very early.

In daily life, it is not difficult to see crystals of various colors and different properties:

Crystals can be divided into:

(1) white crystal: colorless and transparent as water;

(2) Amethyst: purple is transparent or translucent (containing trivalent iron and manganese);

(3) Smoke crystal (commonly known as tea crystal) is a transparent crystal, which is smoky yellow or smoky brown;

(4) Ink crystal: black, translucent crystal containing organic matter;

(5) Topaz: a transparent crystal (containing ferrous iron), yellow to red, orange, yellow and brown;

(6) Barasuishou (also known as "hibiscus stone"): rose, light rose to dense block (containing trace elements such as Ti);

(7) hair crystal: hair-like mineral inclusions containing diamond, hornblende, etc.

(8) Green crystal: needle-like inclusions containing actinolite;

(9) Rainbow crystal: a crystal containing tiny bubbles or quenching bodies to fill cracks, which produces a rainbow by interfering with light. Artificial crystals and rock crystals are both made of silica, and high-purity silica is called "crystal". Crystal is a transparent hexagonal crystal with high hardness and strong reflectivity. Pure crystals are colorless and transparent crystals, which can hardly be found in rock crystals without impurities. Most rock crystals contain bubbles, impurities and crystals are mixed. Artificial crystal is made of quartz sand through a series of processes, fine cutting technology and flawless polishing. The crystal is pure and transparent, which makes up for the deficiency of rock crystal. Adding metal elements such as lead to artificial crystals can enhance the splitting of light and show the nobility of crystals. Due to the complex technology and superb technology, some artificial crystals are even more expensive than those in rock crystals Ultraviolet rays can pass through artificial crystals and rock crystals, but ordinary glass can't. Crystal and ordinary sand are substances that "come out of the womb together". When the silicon dioxide crystal is perfect, it is a crystal; Silica becomes agate after gelatinization and dehydration; Water-containing silica gel becomes opal after solidification; When the particle size of silica is less than several microns, chalcedony, flint and secondary quartzite are formed. Pure colorless and transparent crystal is a variety of seasonable. The chemical composition contains 46.7% silicon and 53.3% oxygen. Because it contains different mixtures or mechanical mixtures, it has many colors. Purple and green are caused by iron (Fe2+) ions, purple can also be caused by titanium (Ti4+), and other colors are caused by color centers. The crystals contain sandy and fragmented goethite, hematite, rutile, magnetite, garnet and chlorite. Hair crystals are formed by inclusions containing hairy needle-like minerals visible to the naked eye. Containing manganese and iron is called amethyst; Iron (golden or lemon) is called topaz; Rose color containing manganese and titanium is called rose time, that is, pink crystal; Smoke color is called smoke crystal; Brown is called tea crystal; Black and transparent are called ink crystals.