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:

Chemical Formula	SiO2, Silicon dioxide
Crystal Structure	a-quartz: trigonal ß-quartz: hexagonal
Color	Colorless, various colors from clear to black
Hardness	7
Refractive Index	1.544 – 1.553
Density	2.65; 2.59–2.63 in impure forms
Cleavage	Indistinct
Transparency	Transparent to opaque
Double Refraction or Birefringence	0.009
Lustre	Vitreous, waxy to dull
Fluorescence	Usually none
Mineral Class	Quartz

Classification:

• Rutilated quartz
• Smoky quartz
• Brown smoky quartz
• Rose quartz
• Lemon quartz