Rock Crystal

Definition and formation

Natural crystal is a crystalline body of the mineral Quartz, chemically composed of silica (SiO₂), which is formed through a long natural process under specific geological conditions. It is usually formed by the orderly arrangement of silicon atoms and oxygen atoms in a siliceous solution-rich environment with high temperature, high pressure and siliceous solution in the underground area, and gradually crystallized and grown. For example, in some volcanic areas or rock fissures, silica-rich hydrothermal fluids slowly cool and precipitate, eventually forming natural crystal crystals over thousands of years or more.

Physical

• Appearance: Natural crystal crystals have regular geometric shapes, common columnar, rhombohedral shapes, etc., and the crystal surface is usually relatively smooth, with natural crystal luster. They vary widely in size, from small ones that can be as small as a few millimeters to large ones that can be several meters long, although large, high-quality natural crystals are rare. For example, in some crystal mines, people can find natural crystal clusters of various shapes and sizes, which grow together to form a spectacular scene.
• Transparency and luster: generally with high transparency, some are as clear as water, and some may be slightly hazy due to impurities and other factors. Its luster belongs to the glass luster, which can reflect bright light under the illumination of light, and looks crystal clear and very textured. Like high-quality natural white crystal, it is extremely transparent, and looks like pure ice cubes when viewed to light.
• Hardness: The Mohs hardness is about 7, which is relatively hard, and can easily leave scratches on minerals with lower hardness such as gypsum and calcite, but it can also be scratched by harder substances such as diamonds and corundum. For example, if you cut glass with natural crystal, there will be obvious scratches on the surface of the glass, but the crystal itself will not be damaged, which is also an easy way to identify natural crystal (although it needs to be distinguished from other materials of similar hardness).
• Density: The density is around 2.65 grams per cubic centimeter, which may fluctuate slightly depending on the impurities contained inside. By measuring the density, it can be used to determine whether it is a natural crystal to a certain extent, but this method requires more accurate measuring instruments and a comprehensive judgment in combination with other identification methods.
• Optical properties: It has the phenomenon of double refringence, that is, when the light passes through the natural crystal, it will be decomposed into two refracted rays, which makes the natural crystal have a certain application value in the field of optical instruments. At the same time, its refractive index is relatively stable, between 1.544 – 1.553, and the refractive index of natural crystals of different colors and origins will be slightly different, which can be used as one of the important identification bases in the field of gem identification.

Color variety

• Colorless crystal (White or Clear Crystal): also known as white crystal, is the most common type of natural crystal, pure and transparent, almost free of impurities and color-causing elements, often used to make crystal jewelry basic materials, or processed into a variety of crystal handicrafts, such as white crystal carved Buddha statues, zodiac ornaments are more common in the market, because of its pure and elegant appearance, very popular with people.
• Purple crystal (Amethyst): Because it contains trace amounts of iron (Fe), manganese (Mn) and other impurity elements, it presents different shades of purple, ranging in color from light purple to dark violet, and is often called amethyst. Amethyst is widely used in the field of jewelry, can be made into necklaces, bracelets, rings and other jewelry, its mysterious and elegant purple gives the jewelry a unique beauty, favored by consumers, such as the famous Uruguayan amethyst, rich and bright color, high quality, is a high-quality variety of amethyst.
• Yellow crystal (Citrine): Mainly due to the presence of iron (Fe), it exhibits a color ranging from light yellow to golden yellow, and is also called citrine. Citrine is often regarded as a symbol of wealth in the market, so it is used more in commercial jewelry, such as ornaments made into fortune or citrine jewelry to wear, among which Brazilian citrine is famous for its bright color and transparent crystals.
• Pink crystal (Rose Quartz): Because it contains trace amounts of titanium (Ti), iron (Fe) and other elements, it shows a soft pink color, also known as pink quartz or hibiscus stone. It is often given the meaning of love, and is a popular material for making couples’ jewelry and women’s jewelry, such as pink quartz bracelets, etc., because of its pink color gives people a warm and romantic feeling, and is very popular with young women.
• Smoky Quartz: It contains traces of aluminum (Al), lithium (Li) and other elements, which make the crystal show a smoky gray hue from light brown to dark black, and the appearance looks as if it has been smoked, hence the name. Smoke crystal is often used to make some jewelry or handicrafts with a simple and calm style, such as smoky quartz carved seals, etc., which have a unique charm.
• Green Quartz: Relatively rare, its color formation may be related to the presence of trace amounts of chromium (Cr) and other elements, showing a fresh green color, but many so-called green crystals on the market may have been artificially irradiated and other treatments, which need to be carefully identified. Natural green crystals can be used to make some unique jewelry that shows off the beauty of nature like no other.

Internal features

• Inclusions: Natural crystals often contain a variety of inclusions, which are formed by encapsulating surrounding minerals, gases, liquids and other substances during the formation process. Common types of inclusions are:
  • Gas-liquid inclusions: Presenting in the shape of a circle, oval, etc., containing gas and liquid, when observed under the microscope, it is like a small bubble in the liquid, such as some natural crystals can see the distribution of small gas-liquid inclusions in groups, which is one of the important bases for judging that it is a natural crystal.
  • Mineral inclusions: such as rutile, actinolite, tourmaline and other mineral crystals are wrapped inside the crystal, these mineral inclusions vary in shape, size and distribution, some are needle-like, filamentous (like rutile inclusions are often hair-like in crystals, which is often called “hair crystal“), and some are lumpy, etc., adding unique ornamental value and identification characteristics to natural crystals.
  • Negative crystal: It is a cavity similar to the shape of the crystal formed in the growth process of the crystal crystal, and its shape is related to the crystal plane shape of the crystal itself, usually presented as rhombohedral, hexagonal columnar and other shapes, the interior is generally empty, and may also contain some impurities, which is also one of the internal characteristics that need to be paid attention to when identifying natural crystals.
• Growth texture: The growth of natural crystal has a certain regularity, which will leave growth textures, which are usually continuous and irregular, and may show bending, twisting and other forms, which are obviously different from the more regular and parallel growth textures of synthetic crystals. By observing the growth textures, it can be used to help distinguish between natural and synthetic crystals, such as using tools such as microscopes to carefully observe the texture trends and characteristics on the surface and inside the crystals.

Distribution of origins

• Brazil: It is one of the most important natural crystal producing areas in the world, producing a wide variety of crystals and excellent quality. Brazil’s crystal ore reserves are large, like its Minas Gerais and other places are rich in amethyst, citrine and other high-quality crystals of various colors, whether it is crystal transparency, color or size, there are many excellent works, and Brazilian crystal occupies an important position in the international market, loved by crystal lovers and jewelers around the world.
• Uruguay: Famous for producing high-quality amethyst, Uruguayan amethyst is rich and deep in color and has high crystal purity, and is often regarded as the top variety of amethyst. The country’s crystal mines are mainly located in the northern region, and its unique geological conditions have produced high-quality amethyst, and in the international crystal and jewelry market, Uruguayan amethyst tends to be relatively expensive, making it one of the preferred materials for making high-end amethyst jewelry.
• China: Natural crystal resources are also relatively abundant, and they are distributed in many provinces. For example, Donghai County, Jiangsu Province has the reputation of “crystal capital”, is an important crystal producing area in China, the crystal produced here is mainly white crystal, but also other colors of crystal, the output is large and the quality is constantly improving, not only to supply the domestic market, but also a large number of exports to other countries, driving the development of the local crystal processing and trade industry; In addition, Hainan, Xinjiang and other places also have crystal mineral resources, each with its own characteristics, providing a sufficient raw material base for the development of China’s crystal industry.
• Madagascar: The country’s crystal resources are diverse, and many unique crystal varieties have been discovered. The natural crystals produced in Madagascar often have strong local characteristics, and some of the crystal’s color, internal inclusions and other characteristics are different from other origins, which is very popular in the international crystal collection market, attracting many collectors to explore and collect crystal treasures from here.
• Russia: It has abundant crystal minerals, distributed in Siberia and other regions, and the crystals produced are mainly smoky crystals, etc., and its crystal crystals are usually larger, but due to the restrictions of mining and other conditions, the circulation of Russian crystals in the market is relatively not particularly large, but it is still an important part of the world’s crystal resources, and it has important value for studying the geological origin of crystals.

Fields of application

• Jewelry industry: Natural crystal is widely used in the production of various types of jewelry, such as necklaces, bracelets, earrings, rings, pendants, etc., because of its beautiful appearance, diverse colors and cultural implications. Different colors of crystals can be matched with different styles of jewelry to meet the aesthetic needs and emotional sustenance of different consumers, such as necklaces made with amethyst and white crystal, which are both elegant and mysterious, and are very popular with female consumers.
• Handicraft production field: can be carved into a variety of exquisite handicrafts, such as crystal ornaments, carvings, etc., showing unique artistic value. Carvers use the transparency, hardness and other characteristics of crystal, through exquisite skills to carve it into Buddha statues, figures, animals, landscapes and other themes of the work, in the handicraft market is highly favored, some high-quality crystal handicrafts even have a high collection value.
• Optical instrument field: with its birefringence, relatively stable refractive index and other optical properties, natural crystal also has a certain application in optical instruments, such as the production of optical lenses, prisms and other components, but with the development of synthetic crystal technology, in some large-scale industrial applications, synthetic crystals gradually occupy more share, but natural crystals are still used in some high-end optical instruments with special requirements for optical properties and natural characteristics.
• Feng Shui Culture and Energy Healing (although lacking scientific evidence, it has a certain influence in folk culture): In some Feng Shui theories, natural crystals of different colors are believed to have different powers and functions, such as pink quartz is believed to bring love luck, citrine is believed to bring fortune, etc.; In terms of energy healing, some people claim that natural crystals can regulate the body’s aura, relieve stress, etc., but these claims have not been rigorously verified by science, and are more present in folk culture and the concept of partial alternative therapy.

Identification methods

• Observe the appearance and internal characteristics: carefully check whether the transparency and color of the crystal are natural and uniform, and whether there are natural inclusions and irregular growth textures inside, etc., as mentioned earlier, the inclusions of natural crystals have different shapes and irregular distributions, and the growth textures are also natural and continuous and have bending and torsion, which is obviously different from synthetic crystals.
• Test hardness: Using the characteristics of natural crystal hardness of about 7, it can be used to scratch glass and other materials with low hardness, if it can easily leave scratches on the glass, and it is basically undamaged, it may be natural crystal, but it needs to be further distinguished from other materials with similar hardness, such as topaz hardness is also close to 7, so it should be combined with other identification methods to make a comprehensive judgment.
• Measuring density: Through professional density measuring instruments, measure whether the density of the crystal is about 2.65 grams / cubic centimeter, but the density will fluctuate slightly due to internal impurities and other factors, and the measurement requires certain accuracy requirements, so this method is usually used in conjunction with other means to identify natural crystals.
• Use optical instruments to detect: use polarizers, microscopes, spectrometers and other optical instruments to further observe the optical properties, internal structure and spectral characteristics of crystals, for example, natural crystals will appear bright and dark extinction under the polarizer, and the internal inclusions and growth textures can be seen more clearly through the microscope, and the spectrometer can analyze its absorption spectrum to assist in judging whether it is a natural crystal.

In short, as a beautiful mineral crystal containing rich geological and cultural information, natural crystal has an important status and value in many fields, whether it is worn as jewelry, handicrafts or in some specific cultural contexts, it is deeply concerned and loved by people.