Home Gemstone Quartz

Quartz

SHARE

Quartz is one of the most famous minerals on the earth. It occurs in essentially all mineral environments, and is the crucial constituent of many rocks. It is likewise the maximum varied of all minerals, taking place in all distinct bureaucracy, habits, and colorings. There are more range names given to Quartz than any other mineral.

It is the maximum abundant and widely allotted mineral determined at Earth’s surface. It is gift and ample in all parts of the arena. It bureaucracy in any respect temperatures. It is abundant in igneous, metamorphic, and sedimentary rocks. It is highly resistant to both mechanical and chemical weathering. This durability makes it the dominant mineral of mountaintops and the primary constituent of seaside, river, and wilderness sand. It is ubiquitous, ample and durable. Minable deposits are determined at some stage in the world.

Name: The name quartz is a German word of ancient derivation.

Crystallography: Quartz rhombohedral; trigonal-trapezohedral. Quartz hexagonal; trapezohedral. Crystals commonly prismatic, with prism faces horizontally striated. Terminated usually by a combination of positive and negative rhombohedrons, which often are so equally developed as to give the effect of a hexagonal dipyramid. In some crystals one rhombohedron predominates or occurs alone. The prism faces may be wanting, and the combination of the two rhombohedrons gives what appears to be a doubly terminated hexagonal dipyramid (known as a quartzoid). Some crystals much distorted, but the recognition of the prism faces by their horizontal striations will assist in the orientation of the crystal. The trapezohedral faces are to be occasionally observed as small truncations between a prism face and that of an adjoining rhombohedron either to the right or left, forming what are known as right- or left-handed crystals. Crystals are often elongated in tapering and sharply pointed forms, owing to an oscillatory combination between the faces of the different rhombohedrons and those of the prism. Some crystals twisted and bent.

Crystals frequently twinned. The twins are usually so intimately intergrown that they can be determined only by the irregular position of the trapezohedral faces, by etching the crystal, or by the pyroelectric phenomena that they show. The size of crystals varies from individuals weighing a ton to finely crystalline coatings, forming “ drusy ” surfaces. Also common in massive forms of great variety. From coarse- to fine-grained crystalline to flintlike or cryptocrystalline, giving rise to many variety names. May form in concretionary masses.

Composition: Si02. Si = 46.7 percent, 0 = 53.3 percent. Usually nearly pure.

Diagnostic Features: Characterized by its glassy luster, conchoidal fracture, and crystal form. Distinguished from calcite by its high hardness. Maybe confused with some varieties of beryl.

Similar Species: Lechatelierite, Si02, is fused silica or silica glass. Found in fulgurites, tubes of fused sand formed by lightning, and in cavities in some lavas.

Quartz Physical Properties

Chemical ClassificationSilicate
ColorQuartz occurs in virtually every color. Common colors are clear, white, gray, purple, yellow, brown, black, pink, green, red.
StreakColorless (harder than the streak plate)
LusterVitreous
DiaphaneityTransparent to translucent
CleavageNone – typically breaks with a conchoidal fracture
Mohs Hardness7
Specific Gravity2.6 to 2.7
Diagnostic PropertiesConchoidal fracture, glassy luster, hardness
Chemical CompositionSiO2
Crystal SystemHexagonal
UsesGlass making, abrasive, foundry sand, hydraulic fracturing proppant, gemstones

Quartz Optical Properties

PPL. XPL. Quartz grains in sandstone.
Property
Value
FormulaSiO2
Crystal Systemhexagonal
Crystal Habitprismatic hexagonal crystals with horizontally striated faced; sometimes appears dursy: twinning common
Cleavageseldom distinct
Color/Pleochroismcolorless, white, purple, yellow, brown, pink, blue
Optic SignUniaxial (+)
Refractive Indices
omega =
epsilon =
1.544
1.553
Max Birefringence0.009
Distinguishing Featuresuniaxial; low relief; low birefringence
OccurrenceQuartz is extremly common and can be found in many types of igneous, sedimentary, and metamorphic rocks.
EditorsChristine Raczka (MHC ’08), Caroline Hackett (Smith ’14)

Quartz Crystal Habit and Structure

Quartz belongs to the trigonal crystal system. The ideal crystal form is a six-sided prism terminating with six-sided pyramids at every cease. In nature quartz crystals are regularly twinned (with dual proper-surpassed and left-exceeded crystals), distorted, or so intergrown with adjacent crystals of quartz or other minerals as to simplest show part of this shape, or to lack apparent crystal faces altogether and seem huge. Well-shaped crystals commonly form in a ‘bed’ that has unconstrained boom into a void; commonly the crystals are connected at the other stop to a matrix and simplest one termination pyramid is gift. However, doubly terminated crystals do arise in which they develop freely without attachment, as an example inside gypsum. It geode is this kind of state of affairs in which the void is about spherical in form, lined with a mattress of pointing inward.

Occurrence of Quartz

Quartz occurs as an important constituent of those igneous rocks which have an excess of silica, such as granite, rhyolite, pegmatite. It is extremely resistant to both mechanical and chemical attack, and thus the breakdown of igneous rocks containing it yields quartz grains which may accumulate and form the sedimentary rock sandstone. Also occurs in metamorphic rocks, as gneisses and schists, while it forms practically the only mineral of quartzites. Deposited often from solution and is the most common vein and gangue mineral. Forms as flint deposited with chalk on the sea floor in nodular masses. Solutions carrying silica may replace beds of limestone with a granular cryptocrystalline quartz known as chert, or discontinuous beds of chert may form contemporaneously with the limestone. In rocks it is associated chiefly with feldspar and muscovite; in veins with practically the entire range of vein minerals. Often carries gold and becomes an important ore of that metal. Occurs in large amount as sand in stream beds and upon the seashore and as a constituent of soils.

Rock crystal is found widely distributed, some of the more notable localities being: the Alps; Minas Geraes, Brazil; the island of Madagascar; Japan. The best quartz crystals from the United States are found at Hot Springs, Arkansas, and Little Falls and Ellenville, New York. Important occurrences of amethyst are in the Ural Mountains; Czechoslovakia; Tyrol; Brazil. Found at Thunder Bay on the north shore of Lake Superior. In the United States found in Delaware and Chester Counties, Pennsylvania; Black Hills, South Dakota; Wyoming. Smoky quartz is found in large and fine crystals in Switzerland; and in the United States at Pikes Peak, Colorado; Alexander County, North Carolina; Auburn, Maine.

The chief source of agates at present is a district in southern Brazil and northern Uruguay. Most of these agates are cut at Oberstein, Germany, itself a famous agate locality. In the United States agate is found in numerous places, notably in Oregon and Wyoming. The chalk cliffs of Dover, England, are famous for the flint nodules that weather from them. Similar nodules are found on the French coast of the English Channel and on islands off the coast of Denmark. Massive quartz, occurring in veins or with feldspar in pegmatite dikes, is mined in Connecticut, New York, Maryland, and Wisconsin for its various commercial uses.

Coarsely Crystalline Varieties (according to color)

Amethyst (purple quartz) 5 | by James St. John
Amethyst (purple quartz) | by James St. John, flickr.com

Amethyst: Amethyst is a shape of quartz that stages from a shiny to dark or stupid crimson shade. The international’s biggest deposits of amethysts may be located in Brazil, Mexico, Uruguay, Russia, France, Namibia and Morocco. Sometimes amethyst and citrine are discovered developing within the identical crystal. It is then called ametrine. An amethyst is fashioned whilst there’s iron within the location in which it became formed.

Dumortierite in Quartz
Dumortierite in Quartz

Blue quartz: Blue quartz contains inclusions of fibrous magnesio-riebeckite or crocidolite.

Dumortierite quartz: Inclusions of the mineral dumortierite within quartz pieces regularly bring about silky-appearing splotches with a blue hue, shades giving off pink and/or grey colors moreover being found. “Dumortierite quartz” (every so often called “blue quartz”) will now and again feature contrasting light and dark shade zones across the material.Interest in the positive nice kinds of blue quartz as a collectible gemstone in particular arises in India and inside the United States.

citrine crystal
citrine crystal 

Citrine: Citrine is a spread of quartz whose colour levels from a faded yellow to brown because of ferric impurities. Natural citrines are uncommon; maximum commercial citrines are heat-treated amethysts or smoky quartzes. However, a warmth-treated amethyst may have small lines inside the crystal, as opposed to a herbal citrine’s cloudy or smokey appearance. It is sort of impossible to distinguish between cut citrine and yellow topaz visually, however they range in hardness.

Amethyst-milky quartz (Diamond Hill, Ashaway Village, Hopkinton, Rhode Island,
Amethyst-milky quartz (Diamond Hill, Ashaway Village, Hopkinton, Rhode Island,

Milky quartz: Milk quartz or milky quartz is the most not unusual kind of crystalline quartz. The white colour is due to minute fluid inclusions of gasoline, liquid, or each, trapped at some point of crystal formation, making it of little value for optical and first-rate gemstone packages.

Rose quartz is a type of quartz which exhibits a pale purple to rose red hue. The color is commonly taken into consideration as due to hint quantities of titanium, iron, or manganese, inside the fabric. Some rose quartz includes microscopic rutile needles which produces an asterism in transmitted light. Recent X-ray diffraction research recommend that the shade is because of skinny microscopic fibers of likely dumortierite within the quartz.

Smoky quartz Ural Berezovski (Sverdlovsk Oblast)

Smoky quartz is a grey, translucent model of quartz. It ranges in readability from nearly entire transparency to a brownish-grey crystal that is almost opaque. Some also can be black. The translucency outcomes from herbal irradiation creating free silicon within the crystal.

Prasiolite - Green Quartz
Prasiolite – Green Quartz

Prasiolite: Not to be harassed with Praseolite. Prasiolite, also referred to as vermarine, is a ramification of quartz that is inexperienced in coloration. Since 1950, almost all natural prasiolite has come from a small Brazilian mine, however it is also visible in Lower Silesia in Poland. Naturally taking place prasiolite is also observed inside the Thunder Bay location of Canada. It is a unprecedented mineral in nature; maximum inexperienced it is warmth-handled amethyst

Cryptocrystalline Varieties

The cryptocrystalline varieties of quartz may be divided into two general classes; namely, fibrous and granular, which, in most cases, are impossible to tell apart without microscopic aid.

Fibrous Varieties

Chalcedony is the general name applied to fibrous varieties. It is more specifically thought of as a brown, translucent variety, with a waxy luster, often mammillary and in other imitative shapes. Chalcedony has been deposited from aqueous solutions and is frequently found lining or filling cavities in rocks. Color and banding give rise to the following varieties:

  1. Carnelian. A red chalcedony.
  2. Chrysoprase. An apple-green chalcedony.
  3. Heliotrope or bloodstone. A green chalcedony with small red spots in it.
  4. Agate. A variegated variety with alternating layers of chalcedony and opal, or granular cryptocrystalline quartz. The different colors are usually in delicate, fine parallel bands which are commonly curved, in some specimens concentric (Plate XIV). Most agate used for commercial purposes is colored by artificial means. Some agates have the different colors not arranged in bands but irregularly distributed. Moss agate is a variety in which the variation in color is due to visible impurities, often manganese oxide in moss-like patterns. Wood that has been petrified by replacement by clouded agate is known as silicified or agatized wood.
  5. Onyx. Like agate, is a layered chalcedony and opal, with layers arranged in parallel planes.
precious stone agate
Precious stone agate

Granular Varieties

  1. Flint. Something like chalcedony in appearance, but dull, often dark, in color. It usually occurs in nodules in chalk and breaks with a prominent conchoidal fracture, giving sharp edges. Used for various implements by early man.
  2. Chert. A compact massive rock similar in most properties to flint, but usually light in color.
  3. Jasper. A granular cryptocrystalline quartz, usually colored red from hematite inclusions.
  4. Prase. Dull green in color; otherwise similar to jasper, and occurs with it.
Replica flint spear
Replica flint spear

Quartz Uses

  • Geological processes have occasionally deposited sands which are composed of virtually one hundred% quartz grains. These deposits have been identified and produced as sources of excessive purity silica sand. These sands are used within the glassmaking enterprise. Quartz sand is used inside the production of field glass, flat plate glass, uniqueness glass, and fiberglass.
  • The high hardness of quartz, seven at the Mohs Scale, makes it more difficult than most different natural materials. As such it’s miles an wonderful abrasive cloth. Quartz sands and finely floor silica sand are used for sand blasting, scouring cleansers, grinding media, and grit for sanding and sawing.
  • It may be very proof against both chemical compounds and heat. It is therefore frequently used as a foundry sand. With a melting temperature better than maximum metals, it is able to be used for the molds and cores of commonplace foundry work. Refractory bricks are often made of quartz sand because of its excessive warmth resistance. Quartz sand is likewise used as a flux in the smelting of metals.
  • Quartz sand has a excessive resistance to being beaten. In the petroleum industry, sand slurries are compelled down oil and gasoline wells below very excessive pressures in a technique referred to as hydraulic fracturing. This high strain fractures the reservoir rocks, and the sandy slurry injects into the fractures. The long lasting sand grains keep the fractures open after the pressure is launched. These open fractures facilitate the flow of natural gas into the properly bore.
  • Quartz sand is used as a filler inside the manufacture of rubber, paint, and putty. Screened and washed, carefully sized grains are used as filter media and roofing granules. Quartz sands are used for traction within the railroad and mining industries. These sands also are used in recreation on golfing publications, volleyball courts, baseball fields, kid’s sand boxes and seashores.
  • It makes an terrific gemstone. It is hard, durable, and usually accepts a super polish. Popular sorts of quartz that are widely used as gem stones include: amethyst, citrine, rose quartz, and aventurine. Agate and jasper are also kinds of quartz with a microcrystalline structure.
  • “Silica stone” is an industrial term for materials consisting of quartzite, novaculite, and different microcrystalline include rocks. These are used to provide abrasive gear, deburring media, grinding stones, hones, oilstones, stone files, tube-mill liners, and whetstones.
  • Tripoli is crystalline silica of an exceedingly high-quality grain length (less than ten micrometers). Commercial tripoli is a almost pure silica cloth this is used for a diffusion of mild abrasive purposes which encompass: soaps, toothpastes, metallic-sprucing compounds, rings-sharpening compounds, and buffing compounds. It can be used as a polish while making tumbled stones in a rock tumbler. Tripoli is likewise used in brake friction merchandise, fillers in teeth, caulking compounds, plastic, paint, rubber, and refractories.

Distribution

Extraordinarily common.

  • Fine specimens from many places in the Alps of Switzerland and Austria.
  • At Carrara, Tuscany, Italy.
  • From Bourg d’Oisans, Isµere, France. At Mursinka, Ural Mountains, in the Dodo mine, about 100 km west-northwest of Saranpaul, Subpolar Ural Mountains, and elsewhere in Russia.
  • From Sakangyi, Katha district, Myanmar (Burma).
  • Large twins from Yamanashi Prefecture and many other places in Japan.
  • At Tamboholehehibe and elsewhere in Madagascar.
  • From Brazil, in large amounts from many localities in Rio Grande do Sul, Minas Gerais, Goilas, and Bahia.
  • Around Artigas, Uruguay. At Thunder Bay, Lake Superior, Ontario, Canada.
  • In the USA, from Mt. Ida to Hot Springs, Ouachita Mountains, Arkansas; at Middleville, Herkimer Co., New York; in North Carolina, especially in Alexander and Lincoln Cos. From the Pala and Mesa Grande districts, San Diego Co., California; the El Capitan Mountains, Lincoln Co., New Mexico; the Crystal Park area, Beaverhead Co., and Little Pipestone Creek, Je®erson Co., Montana; and in the Pikes Peak area, El Paso Co., Colorado. From Mexico, in Veracruz and Guerrero.

References

  • Bonewitz, R. (2012). Rocks and minerals. 2nd ed. London: DK Publishing.
  • Dana, J. D. (1864). Manual of Mineralogy… Wiley.
  • Handbook of Mineralogy. [online] Available at: http://www.handbookofmineralogy.org [Accessed 4 Mar. 2019].
  • Mineral information, data and localities.. [online] Available at: https://www.mindat.org/ [Accessed. 2019].
  • Smith College. [online] Available at: https://www.smith.edu/academics/geosciences [Accessed 15 Mar. 2019].
Cite this article as: Geology Science. (2019). Quartz. [online] Available at: http://geologyscience.com/minerals/quartz/ [21st October 2019 ]