Quartz

Quartz Crystal found at Hansen Creek (west of Snoqualmie Pass)

WHAT IS IT?

• Silicon Dioxide (Si02) - Constitutes 12% of the earth’s crust (2nd most abundant mineral after feldspar, which constitutes up to 60%)

HISTORY

• The name is derived from the German word "Quarz'. The Middle High German name is “twarc", which has roots to the Slavic word “Tvrdy", meaning "hard"

• The Chinese used smokey quartz to make sunglass lenses in the 12th century

• Used by ancient Mediterranean cultures (Minoan, Roman, Greek) for impression seals (intaglios), jewelry and tools (knives)

TYPES OF QUARTZ

• There are many varieties (some are semi-precious gemstones). This is an incomplete list:

  • Agate- multi-colored, banded, translucent or semi-translucent chalcedony

  • Amethyst - clear purple colored quartz containing trace amounts of iron with transition metals

  • Ametrine - a combination of amethyst & citrine

  • Aventurine - a green translucent chalcedony that shimmers due to Inclusions (usually containing mica)

  • Carnelian - a translucent, reddish-orange chalcedony

  • Chalcedony - a white or light colored material consisting of a mixture of cryptocrystalline quartz (microscopic crystals) & moganite

  • Citrine - quartz that contains iron pigmentation resulting in a yellow to brown color. It is indistinguishable from yellow topaz except for hardness (topaz is harder).  It is often made by heat-treating amethyst or smokey quartz

  • Chrysoprase- a green variety of chalcedony that is colored by nickel oxide

  • Dumortierite quartz — quartz that contains dumortierite crystals (fibrous aluminum-boro silicate)

  • Heliotrope or Bloodstone — a green variety of chalcedony containing red inclusions of iron oxide

  • Jasper - a cryptocrystalline opaque variety that typically has a red or brown color

  • Milky quartz - an opaque white appearance that is caused by minute inclusions of liquid, gas, or a combination of the two. It is the most common variety of quartz and is found almost anywhere.

  • Mtorlite or Chrome Chalcedony — a green variety of chalcedony that gets its color from chrome

  • Onyx is a form of agate that has parallel evenly spaced bands of black and white

  • Prasiolite (aka green quartz or vermarine) - a rare green form of quartz once mined in Brazil & Poland, now only synthetic

  • Rock crystal or clear quartz - colorless & transparent (clear)

  • Rose quartz - a dull pink to rose colored variety that contains iron, manganese, and/or titanium. A rarer variety contains phosphorus and aluminum. Some exhibits diasterism (displays a luminous star pattern when illuminated from back)

  • Sardonyx - similar to onyx but has brown, orange, red, and white banding

  • Smoky quartz - varies from being translucent gray to an almost opaque grey-brown due to natural irradiation. There are a number of varieties (e.g._ Moran, Cairngorm). Contains uranium trioxide

  • Tiger's eye - a fiberous variety that exhibits chatoyancy and is usually orange to red-brown in color

• Quartz-like or quartz derived silica minerals:

  • Coesite — danse polymorph of quartz found at meteorite impact Sites

  • Cristobalite — high-temp polymorph of quartz found in volcanic rock

  • Lechatelierite — an amorphous silica glass formed by lightning strikes

  • Moganite — a monoclinic polymorph of quartz discovered in 1984 (has same chemical composition, but a different structure). Typically constitutes from less than 5% to more than 20% of the mass of a typical chalcedony

  • Stishovite — a very dense polymorph of quartz found at meteorite impact sites (denser than coesite)

  • Tridymite — another high-temp polymorph of quartz found in volcanic rock

WHERE IS IT FOUND?

• Quartz is found worldwide (e.g. most beach sand contains it; granite contains it). Agate, jasper, and milky quartz are common.

• Amethyst— Brazil, Mexico, Uruguay, Russia, France, Namibia and Morocco (best sources)

• Aventurine —Austria, Brazil, Chile, India, Spain, Russia, Tanzania

• Carnelian — Brazil, India, Uruguay

• Citrine — Brazil

• Chrysoprase — Australia, India, Russia, USA

• Heliotrope — India primarily. Also, Australia, Bran, China, Scotland (Isle of Rum), USA

• Onyx — Brazil, Madagascar, Uruguay

• Parsiolite — no current natural sources. Made by heat-treating amethyst and citrine (primarily from Brazil)

• Rose quartz - Brazil, Madagascar, India, United States, Japan, Africa, Germany and Switzerland

• Sardonyx — Brazil, Czech Republic, Germany, Sri Lanka, Uruguay, USA (Great Lakes, Oregon)

• Smoky quartz— Australia, Brazil, Canada, China, England, Ghana, Hungary, India, Madagascar, Mozambique, Scotland, Slovakia, Sweden, Switzerland, and the United States (in numerous states, esp. Arkansas; also Crystal Park near Dillon, MT)

WHAT IS IT USED FOR?

• Jewelry, carvings, collector specimens, heat lamps, prisms, lenses, paints, refractories, abrasives, precision instruments

• Has piezoelectic properties - useful for electronic oscillator crystals (digital watches, computers & radios) & sensors