Quartz
Silicon
dioxide
SiO2
Quartz
is the most abundant and most common mineral on the Earth. It is found
in almost every geological environment and also it is at least a
component of almost every rock type. It has a hexagonal crystal
structure and is made of trigonal crystallized silica. It is most
varied in terms of varieties, colors and forms.
The most important distinction between the types of quartz is that
one is of macrocrystalline, which is individual crystal visible to the
unaided eye, and the other is microcrystalline or cryptodrystalline
varieties, aggregates of crysstals visible only under high
magnification. Chalcedony is the generic term for cryptocrystalline
quartz. The transparent variety tends to be macrocrystalline and the
cryptocrystalline varieties are either translucent or mostly opaque.
The name "quartz" has been derived from the German "Quarz,"
a Slavic origin. It is the most common material identified as mystical
substance maban in the Australian Aboriginal mythology. Pliny the
Elder, a Roman naturalist believed quartz to be a permanently frozen
ice. According to him, quartz is found near glaciers in the Alps and
that the crystals of quartz were fashioned into spheres to cool the
hands. It was also known to him the ability of quartz to split light
into a spectrum.
Nicolas Steno's study of quartz made way for the modern
crystallography. His discovery states that no matter how distorted a
quartz crystal is, the long prism faces always made a perfect 60
degree angle.
Physical Properties of Quartz
| Color |
Clear (in pure form) |
| Crystal habit |
6-sided prism ending in 6-sided
pyramid (typical) |
| Crystal system |
Trigonal |
| Cleavage |
None |
| Fracture |
Conchoidal |
| Mohs scale hardness |
7 - lower in impure varieties |
| Luster |
Vitreous |
| Refractive index |
1.544-1.553 - Dr +0.009 (B-G
interval) |
| Streak |
White |
| Specific gravity |
2.65 constant; variable in
impure varieties |
| Melting point |
1650 (±75) °C |
| Boiling point |
2230 °C |
| Solubility |
H2O insoluble |
Molecular Weight of Quartz
| Silicon |
46.74% (Si) |
100.00% (SiO2) |
| Oxygen |
53.26% (O) |
|
|
100.00% |
100.00% = Total Oxide |
Major Varieties of Quartz
Chalcedony
- Any of the cryptocrystalline quartz, although usually only used for
white or lightly colored material.
Agate - Banded Chalcedony, translucent.
Onyx - Agate, where bands are straight, parallel and also consistent
in size.
Jasper - Opaque chalcedony, impure.
Aventurine - Translucent chalcedony with a smaller inclusions
(generally mica), which shimmer.
Tiger's Eye - Fibrous quartz, exhibiting chatoyancy.
Rock Crystal - Clear, colorless.
Ruby Quartz - Crimson glass-like crystal that absorbs vast amounts of
solar energy.
Amethyst - Purple, transparent.
Citrine - Yellow to reddish orange, greenish yellow.
Rose Quartz - Pink, translucent, might display diasterism.
Milk Quartz or Snow Quartz - White, translucent to opaque, may
display diasterism.
Smoky Quartz - Brown, transparent.
Morion - Dark-brown, opaque.
Carnelian - Reddish orange chalcedony, translucent.
Uses of Quartz
- Silica
for glass
- Electrical
components
- Optical
lenses
- Abrasives
- Gemstones
- Ornamental
stone
- Building
stone
- Piezoelectricity
- It creates electricity through a process known as piezoelectricity
with mechanical stress given on it. Earlier, quartz crystal was uses
as phonograph pickup. Now, it is used as a crystal oscillator. These
oscillators are simply known as "quartzes."
Occurrences of Quartz
- Amethyst
- Brazil, Uraguay, Mexico, Russia, Thunder Bay area of Canada, and
some localities in the US.
- Smoky
Quartz - Brazil, Colorado, Scotland, Swiss Alps and many other
places.
- Rose
Quartz - It is widespread but large quantities come from Brazil.
- Natural
Citrine - It is found with many amethyst deposits but in a very rare
quantities.
- Rock
Crystal - Brazil, Arkansas, many localities in Africa, etc.
- Fine
Agates - Brazil, Lake Superior region, Montano, Mexico and Germany.
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