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The quarts group of gemstones
Minerals in the quarts group are perhaps the most abundant minerals on earth. The great mountains on earth are partly made up of quarts. These minerals have a simple chemical composition. They consist chemically of silicone and oxygen atoms bounded together in a crystal or glass matrix. Even though quarts minerals are very common and cheap, good specimens of quarts minerals are very fine gemstones.
Crystallic quarts minerals are fairly hard, grade 7, grade 10 is the hardest possible. The group consist of the following special kinds of minerals used in jewelry or as material in other finer utensils.
Ordinary white quarts:
This is the most abundent form of quarts, and is most often simply called
quarts. It consists of colourless small crystals lumped firmly togeather forming
big white, corny, transcucent specimens. Ordinary quarts may look like marble,
and is often mistaken for marble.
Rock crystal: This is big and clear crystal of quarts. They are fine to form with facets like a diamond. A cut rock crystal does not look like a diamond, but has a beauty of its own caracterized by a special kind of transparent clearity.
Citrine: Citrine is a big and transparent crystalsof quarts with red, yellowish or brown colour substances. These substances often contain iron ions.
Rose quarts: A specimen of rose quarts consist of small crystals firmly lumped together and containing red coloured substances. Rose quarts is not transparent, but only translucent and has a corny structure.
Aventurine: Aventurines are fine-crystalled stones mostly consisting of quartz, but with inclusions of other type of mineral crystals, giving the stone a shimmering appearance and with shades of different colors. The dominant color is most often green, but it can be any other color.
Amethyst: This is is big and transparent crystal of quarts with violet substances blended into the crystal matrix.
Chalcedon: Chalcedon is a kind of quartz with very small crystals. It is usually formed by crystallization from watery solutions in hollow formations in rock structures. Often it has a shape like a ball with bigger quartz crustals at the innside and is often hollow in the mid. Chalcedon is ofte gray, but can get shades of nearly any color, often in layers, or be brightly colored too. According to color pattern chalcedons have several names like agate, carneol, tiger eye.
Agate: An agate specimen consists of microscopic crystals, and is therefore not transparent, but is to some extend translucent. The specimen has concentric colour bands deposited one at the outside of the other. Agates have been formed in cavities in rocks, and the bands of the agate has been gradually cystalized onto the walls of the cavity from water in the cavy. The colour bands can be brown, red, blue, grey, orange and any blending of these colours.
Onyx: An onyx specimen also consist of microscopic crystals and is only to some extend translucent. An onyx has coloured layers stacked on at the top of each other. An onyx specimen have been formed by crystallisation from water solutions in rock cavities, like the agate. The colour layers are often green, white, brown and red, with green often being the dominant colour. Sometimes layers are totally black, and cuts from such layers are often used as gemstones in male rings.
Carneol: Also a carneol specimen consist of microscopic crystals. Carneol is deep red and nearly not translucent at all. Also this type of quarts has been gradually crystallized from water solutions.
jasper: Jasper is a stone mainly consiting of opaque quartz. Different parts of the stone has different crystal structure. Some are microcrystalline and some with bigger crystals. The differnt part of the stone also have varying microscopic inclusions of colored elements, iron-rich elements that give those parts a red color, or elements that make the color green or otherwie colorated.
Opal: Opal is not crystalline, but has a glassy structure. The glass have small water drops blended into its structure, and this water causes interference and light breaking, making the opale show up a lot of colours that vary according to the angle of light falling into the stone.
Obsidian: Obsidiane is a glass formed when magma cools in vulacoes. Obsidian often contain small gass bubbles, soluted coloured substances or impurities. Obsidian can be transparent, translucent or totally opaque. The colour is mostly green, white or whitish.