a rock forming mineral, contact metamorphics,
hydrothermal, mesothermal, and epithermal veins
The name is derived from the German "quarz" of Slavic 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.
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
- 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
- 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
Cryptocrystalline: masses made up of either
fibrous or granular aggregates of quartz. Both are tough and
compact, and take a good polish when cabbed.
Chalcedony: 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
- 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.