History & Introduction
Quartz is considered to be an important mineral on earth and forms one of the most
popular gemstone category in the world of colored stones. It is the second most
mineral found in plenty in Earth's crust after feldspars. The name 'quartz' comes
from the German word 'quarz', which likely originated from the Slavic and Polish
words meaning 'hard'. The name is descriptive in regard to quartz being the definitive
mineral that measures 7 on the Mohs scale.
Quartz are mainly found in two varieties, which is further subdivided into other,
more specific varietal names. All quartz gemstones share the same silicon dioxide
(SiO2) chemical composition, still they differ in crystal classes and formations.
Quartz has two main branches they are microcrystalline quartz and cryptocrystalline
quartz. Microcrystalline quartz includes amethyst, hawk's eye, blue quartz, aventurine,
citrine, rock crystal, quartz cat's eye, prasiolite, smoky quartz, rose quartz and
tiger's eye. Microcrystalline quartz is typically transparent to translucent and
forms with larger crystals than cryptocrystalline quartz. Cryptocrystalline quartz
are created with microscopically small crystals that in different cases it is not
seen with magnification.
Quartz gemstones are very striking, hard and durable. In many cases, quartz is fairly
inexpensive and available in very large sizes. There are few varieties of quartz
that are very rare. Quartz is an extremely versatile material and cut and carved
into many shapes and sizes.
Recognizing - There is no single definitive test for recognizing
quartz. There are many tests needed to reach conclusive identification. Many gem
labs use a combination of traditional analysis and advanced instruments when testing
quartz samples. Analysis through traditional examines inclusions and color zoning
are generally found in natural quartz. The use of infrared spectroscopy is to graph
wavelengths of infrared light that quartz stones absorb. Quartz crystals even display
piezoelectric properties; a trait shared with tourmaline and a few other gems. Synthetic
quartz is mainly found in colors that is not occur naturally. In number of cases,
the color is simply too intense and deep to be a natural occurrence.
Availability - Quartz gemstones are available in locations across
the globe. Quartz is a major constituent of granite and other igneous rock. It is
also commonly found in sedimentary rock and is a common component of metamorphic
rock. Good formation of crystals can reach extremely large sizes, many times exceeding
several meters in length and weighing over a hundred kilograms.
Macro crystalline quartz deposits can be found in (but are not limited to) the following
places:
Rock crystal: The Alps, Madagascar, Brazil and the USA
Smoky quartz: Brazil, Madagascar, Scotland, Russia, Switzerland and Ukraine
Amethyst: Brazil, Bolivia, Canada, India, Madagascar, Mexico, Myanmar (Burma), Namibia,
Russia, Sri Lanka, Uruguay and Zambia
Amethyst quartz: Brazil, Bolivia, Canada, India, Mexico, Namibia, Russia, Madagascar,
United States (Arizona), Myanmar (Burma), Sri Lanka, United States (Arizona), Uruguay
and Zambia
Ametrine: Brazil and Bolivia
Citrine: Argentina, Brazil, Russia, Madagascar, Scotland, Namibia, Spain and the
USA
Prasiolite: Brazil and the USA (Arizona)
Rose quartz: Sri Lanka, Brazil, India, Madagascar, Namibia, Mozambique and the USA
Aventurine: Austria, Brazil, India, Tanzania and Russia
Prase: Austria, Finland, Germany and Scotland
Quartz cat's eye: India, Brazil and Sri Lanka
Hawk's eye: Sri Lanka, Brazil and India
Tiger's eye: Australia, South Africa, India, Myanmar, USA, Namibia and Sri Lanka.
Cryptocrystalline quartz deposits can be found in (but are not limited to) the following
places:
Australia: Agate, chrysoprase and bloodstone
Brazil: Agate, chalcedony, carnelian, bloodstone and chrysoprase
China: Agate and bloodstone
India: Agate, chalcedony, chrysoprase, bloodstone and carnelian
Kazakhstan: Chrysoprase
Madagascar: Agate, chalcedony and chrysoprase
Mexico: Agate
Mongolia: Agate
Namibia: Agate, blue chalcedony and chalcedony
Russia: Chrysoprase
Sri Lanka: Chalcedony
Uruguay: Agate, chalcedony and carnelian
South Africa: Chrysoprase
Tanzania: Chrysoprase
Zimbabwe: Chalcedony and chrysoprase
USA: Agate (Montana and Wyoming), chalcedony (California), chrysocolla chalcedony
(Arizona), bloodstone and blue chalcedony (California, Nevada, Oregon
Buying Guide
Color - The color of macrocrystalline quartz is as variable as
the spectrum, however transparent quartz is by far the most common color followed
by white or cloudy quartz. Pink (rose quartz), purple (amethyst), gray or brown
to black (smoky quartz) are among the general. Varieties of cryptocrystalline quartz
are multicolored. In artificial light, quartz does not exhibit a desirable quality.
It gives the best presence during daylight, especially after sunrise and just before
sunset. The rich colors of the gemstone are tend to be the valuable.
Clarity and Lustre - Fine quartz is transparent meaning that the
light passes is able to pass through the stone. In case of translucent quartz, the
light passes through the stone is slightly weakened. The best quality quartz is
"clean", free from inclusions of various sort. As the quartz is available in many,
then little reason to go for stones with inclusions seen through visible eyes, excluding
the ones that define the character of the stone (e.g. cat's eye, hawk's eye or scenic
stones). Luster is glassy to vitreous like the crystals, whereas in cryptocrystalline
forms the waxy to dull, however it is vitreous. Crystals ranges from transparent
to translucent; whereas cryptocrystalline goes from translucent or opaque.
Cut and Shape - Due to the roughness of the color distribution
in the crystals, many times quartz is cut in brilliant rounds to maximize their
color. Other cuts used are while the color is better distributed. Quartz is found
in a wide range of calibrated shapes and sizes that adds up to different fancy shapes.
Treatment - Colorless quartz is always not treated. Colored stones
can rarely be enhanced through dyes (as in the case of agate), irradiation (bombardment
due to low level radioactivity), or heating. Few of the stones may also be impregnated
or coated with wax, clear resin and also foil for luster, enhanced color and stability.
Synthetic quartz is even available in plenty. Naturally colored quartz typically
exhibits color zoning.
Gemological Characteristics: