Links To Quartz Information Topics On This Page:
Quartz Varieties And Items in our VIRTUAL GALLERY
Physical Properties
Background Info on Quartz
Occurance and Diagnostic Features
History and Uses
Metaphysical Properties
Quartz (SiO2) is the most abundant single mineral on earth. It makes up about 12% of the earth's crust, occurring in a wide variety of igneous, metamorphic and sedimentary rocks.
Quartz varieties are commonly separated into two groups based on the size of the individual grains or crystals; macrocrystalline quartz in which individual crystals are distinguishable with the naked eye, and cryptocrystalline quartz in which the individual crystals are too small to be easily distinguishable under the light microscope.
Some of the macrocrystalline quartz varieties are: Amethyst, Ametrine, Cat's-eye Quartz, Citrine, Phantom Quartz , Rock Crystal, Rose Quartz, Rutilated Quartz, Smoky Quartz and Strawberry Quartz.
Blue Aventurine Quartz and Green Aventurine Quartz
are actually quartzites (a rock, not a mineral) composed essentially of interlocking
macrocrystalline quartz grains with disseminated grains of other color imparting minerals.
The cryptocrystalline varieties of quartz may be separated into two types;
fibrous and microgranular. Chalcedony is the general term
applied to the fibrous cryptocrystalline varieties.
Agate is an example of a fibrous cryptocystalline
banded chalcedony variety of quartz. Carnelian, Chrysoprase and bloodstone
are other chalcedony varieties.
Chert is the general term applied to the granular cryptocrystalline
varieties of quartz, of which flint and Jasper are examples.
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Coarsely crystalline quartz is common in many igneous rocks
and is an essential constituent in adamellites, alaskites, granites, granodiorites,
quartz diorites and other similar acidic plutonic igneous rocks.
It is a major constituent in granitic pegmatites where it can form as masses
in the core of the pegmatite or intergrown with potassium feldspar (usually
microcline) as
graphic granite in the outer pegmatite zones.
Massive quartz veins are deposited by
ascending hydrothermal solutions, often forming metaliferous ore deposits.
Quartz veins can also be formed by
metamorphic processes such as the recrystalization of magnesite from
serpentine thereby releasing silica. Open cavities in pegmatites and veins
often contain quartz crystals. Because of crystalline quartz's
mechanical and chemical stability, it endures as detrital grains and
accumulates as sand and pebbles when quartz bearing rocks break down,
leading to the
formation of sandstones and their metamorphic equivalents
quartzites. Most metamorphic rocks contain quartz
either recrystallized or unchanged from the original rock.
Secondary quartz
crystals, usually as rock crystal or amethyst, can form on cryptocrystalline
quartz in cavities and vugs thereby forming geodes.
The cryptocrystalline (crystals too small to be distinguished under the
light microscope) varieties may be separated into two types:
fibrous and microgranular. Chalcedony is the general term
applied to fibrous cryptocrystalline varieties. It forms by deposition
from meteoric groundwater or late hydrothermal solutions at or near the
earth's surface, and is frequently found lining or filling cavities in rocks.
Agate is an example of a fibrous cryptocystalline
banded chalcedony variety of quartz. Carnelian, chrysoprase and bloodstone
are other chalcedony varieties.
Chert is the general term applied to the microgranular varieties of quartz.
It is thought to form by the replacement of calcareous rock by silica-rich
solutions, or by direct marine precipitation of silica gel or organic silica.
Jasper is an example of a granular microcrystalline
chert variety of quartz. Jasper's typical reddish brown color is due to
hematite impurities.
Quartz crystals are recognized by their crystal habit, striations, hardness, glassy luster, conchoidal fracture, occurance and general lack of cleavage. Cryptocrystalline varieties are characterized by their hardness, conchoidal fracture, occurance, specific gravity, refractive index and vitreous to greasy luster.
Return to the Index of Quartz Information TopicsThe gem varieties of quartz have been used as gemstones and other ornamental objects for thousands of years. Polished rock crystal spheres or crystal balls were used as a means of divination or scrying in medieval times. For thousands of years before this, quartz crystals and objects made from them were used for divination, disease diagnosis and for awareness of current events in distant places in many ancient cultures.
Flint firemaking tools have been found dating back to the neolithic era. Chipped flint projectile points dating back 40,000 years have been discovered in Mousterian sites in western Europe. Some of the earliest primitive stone tools (axes) fashioned by man's ancestors 2.5 million years ago in the Omo valley in Ethiopia, were made of quartz varieties such as chalcedony, agate, quartzite, flint and chert. These materials were used because of their hardness and their isotropic brittleness which made it possible to shape the tools with relative ease.
Quartz is used today in the manufacture of abrasives, concrete, cements,
porcelain, paints and glass. It is also used as a chemical raw ingredient
in the manufacture of numerous industrial materials. As quartzite and
sandstone it is used as a building material. Untwinned rock crystal quartz is made into lenses and
prisms for optical instruments. Due to its piezoelectric properties, it is
used as a radio oscillator to control
transmission and reception on fixed frequencies. This same property is utilized
in watches and clocks where a tiny quartz plate is used to control
precisely the radio frequency of the electronic circuitry, thus telling the
exact time.
The name quartz comes from a Saxon word meaning cross vein ore.
Each variety of quartz has its own metaphysical characteristics and properties. Please see our information pages for each quartz variety such as amethyst, elestial quartz or rock crystal for their unique metaphysical properties.
For more in-depth metaphysical information, see our Metaphysical Books section.
This is the end of our Quartz Factsheet and Information page.