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, and have the chemical formula SiO2. 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 corny 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.

Corny quarts with other colors: Corny masses of quarts can show many colors. Brown variants are often called smoke quartz. Variants with reddish color is usually called rose quartz. These variants are like the white quartz not transparent, but only translucent.

Aventurine: This is a noble rock art mostly composed of corny quartz. There are also small flat grains of other minerals with a metallic shimmer, for example the crom-compound fuchsite, giving the whole stone a metallic green or blue shine. The basic color of aventurine is most often green, but it can also be orange, brown, yellow or gray.

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.

Amethyst: This is is big and transparent crystal of quarts with violet substances blended into the crystal matrix.

Quartz crystals with other colors: Big quartz crystals can show any color. Those with brown color are usually called smoke quartz, and those with reddish color rose quartz, just like the colored corny quartz masses.

Calcedon: A specimen of calcedon consists of a myriad of microscopic crystals. Calcedon is translucent and have a uniform greyish or grey-blue color and show a calm silky luster. Calcedon grows inside cavities by gradual crystallization from a watery solution. The center of the specimen is often still hollow, and the innermost layer often consists of rock crystal.

Agate: An agate specimen consists as calcedon 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 consists of microscopic crystals and is only to some extend translucent. An onyx has coloured layers stacked upon the top of each other, but the layers lay more regularly and parallelly than in ordinary agate, and there tend to be only few layers. All the layers together often bow in a wavelike fashion. Most colors can occur in onyx, except blue or purple. Black or white layers are common. An onyx specimen have been formed by crystallisation from water solutions in rock cavities, like the agate.

Jewelers often cut out pieces with specific colors and use these as gemstones, especially in rings for men. In the jewelry trade the name "onyx" is most often used about Such pieces in black or other specific colors. The term "onyx" is also used about marble-related rock types, which are not quartz-related, with the same pattern of stacked multicolored layers. This material which often shows shades of green is commonly used in artworks.

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.

Opale: 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.