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SiO2 -
Silicon Dioxide


Hexagonal (excellent hexagonal prisms with termination, also massive, and crypto-crystalline varieties)




yellow - orange




Refrac. Index:

1.54 - 1.55





Spec. Grav.:







a rock forming mineral, contact metamorphics, hydrothermal, mesothermal, and epithermal veins


feldspars, pyrite, tourmaline, rutile


| Largest crystals, Brazil | found virtually everywhere | Ark., USA |


The name is derived from the German "quarz" of uncertain origin. It was called "krystallos" by the Greeks, but this later became the generic term for crystal. It is used as an oscillator in time pieces and in radio, and was mined extensively in brazil during W.W.II. The material has now been synthesized in the laboratory and is much purer and better for electronic use.

Gem info:

Quartz is the most abundant mineral on earth and is present in many rock types. It is classified by both color and physical makeup. First there are two physical types:
1.) crystalline (natural and synthetic)

Crystalline: meaning large single crystals of aggregates of individual crystals. Having the hexagonal shape or habitat of the mineral. (Rose quartz is a minor exception as it rarely forms good crystals.)

  • Amethyst: lilac or purple quartz gets its color from an iron impurity (Fe+3), it is the most valuable of the quartz gem stones. The best quality is dark purple with a red-flash. At one time it was one of the most expensive stones on earth, but with the huge finds in the new world (especially Brazil) the price plummeted.
  • Citrene: yellow to orange in color, citrene gets its color from an iron impurity too, and heating amethyst to 550 degrees centigrade converts it to citrene. Subjecting citrene to radiation can re-convert it to amethyst. Heat treated stones tend to have a red-tint. It is sometimes passed off as a form of topaz being called "bahia-topaz" , "golden topaz" or "Madeira topaz". All of these materials a quartz and NOT topaz. Citrene is typically not as expensive as amethyst, so is usually very inexpensive.
  • Smoky Quartz: smoky quartz gets its color from irradiated impurities which have a smoky area around them. The term "cairngorm" is used to describe the variety found in the Cairngorm Mountains of Scotland. It is very inexpensive in cut stones, less than $1 per carat.
  • Rose Quartz: this is one of the more rare types of crystalline quartz, it is usually somewhat cloudy due to the inclusion of rutile crystals. Large cut stones are rare, and even small ones tend to be cloudy looking. It tends to have more value as a carving material.

Cryptocrystalline: masses made up of either fibrous or granular aggregates of quartz. Both are tough and compact, and take a good polish when cabbed.
the general term used to describe the fibrous variety of cryptocrystalline quartz.

  • Agate: usually a banded material that is translucent and may contain any number of colors or combinations. It may also include members that are non-banded, but contain dendrites in the form of moss or other organic-like structures.
  • Carnelian and Sard: are solid colored, but translucent chalcedony that are in the red to brown end of the spectrum
  • Aventurine : A greenish quartz with fuchite mica or other metallic looking inclusions that make the material "sparkle".
  • Bloodstone : Also known as heliotrope or plasma, is an opaque green chalcedony with red iron oxide inclusions that resemble blood.
  • Chrysophrase: a green variety of chalcedony colored by the element nickel. The best material is now coming from Australia.
  • Onyx: a variety of agate with parallel bands of color that are linear and not in the form of curves. (There is a variety of marble that is sometimes called onyx, but is much softer and easily damaged by acid.)

Jasper, Flint, and Chert are names used to describe some of the varieties of granular quartz.

  • Jasper: it is the granular counterpart of carnelian and sard, and is usually brown, red, yellow, and may have inclusions of metal oxides. The name derived from the Greek and means "spotted stone". Sometimes as parallel lines rather than spots. Several varieties can create what looks like miniature landscape scenes and are often referred to as "picture jaspers".
  • Flint and Chert: non-gem varieties of cryptocrystalline-granular quartz. They chip very easily and thus can be made to hold and edge. Used mainly in the manufacture of arrow heads and stone knives.

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