Quartz Value, Price, and Jewelry Information

Quartz, Tibet - By JJ Harrison (Own work) [CC-BY-SA-2.5], via Wikimedia Commons

Quartz

An overview on Quartz Jewelry and Gemstones. Covers details and essential information on the physical properties and characteristics of a Quartz mineral.

Quartz Value

Quartz is common, except Dumortierite quartz which is somewhat rare.

The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.

Gold In Quartz Value via Gem Price Guide

Accompanying value information:
Cabochons All sizes
to /ct.

Quartz Value via Gem Price Guide

Smoky Quartz All sizes
Faceted to /ct
Rose Quartz All sizes
Faceted to /ct
Rutilated & Tourmalinated Quartz All sizes
Faceted to /ct
Cabochons /ct
Quartz with Lepidocrite All sizes
Faceted or cabochon to /ct
Star Quartz All sizes
to /ct

Quartz Information

Data Value
Name Quartz
Varieties Amethyst, Ametrine, Aqua Aura, Chalcedony, Agate, Fire Agate, Iris Agate, Binghamite, Bloodstone, Carnelian, Chrome-Chalcedony, Chrysocolla Chalcedony, Chrysoprase, Jasper, Dallasite, Orbicular Jasper, Plasma, Onyx, Sardonyx, Petrified Wood, Pietersite, Sard, Citrine, Iris Quartz, Mystic Quartz, Prase, Prasiolite, Quartzite, Aventurine, Rock Crystal, Rose Quartz, Rutilated Quartz, Smoky Quartz, Morion, Tiger's Eye, Falcon's Eye, Tourmalinated Quartz
Colors Colorless, white, gray (various shades) and many shades of yellow, orange, red, brown, purple, violet, blue, pink, green, and black.
Crystallography Hexagonal (R). Occurs in a wide variety of crystal forms, up to large size; also as crystalline masses, cryptocrystalline, granular, in veins and stringers.
Refractive Index 1.544–1.553
Luster Vitreous (crystalline varieties); greasy, waxy (cryptocrystalline varieties).
Polish Luster Vitreous.
Fracture Luster Vitreous.
Hardness 7
Wearability Very Good
Fracture Conchoidal to uneven, granular in aggregates
Specific Gravity 2.651 (very constant); in chalcedonies, up to 2.91.
Birefringence 0.009 (some chalcedonies 0.004)
Cleavage None or indistinct
Dispersion 0.013
Stone Sizes Aggregates to very large. Rock crystal, citrine, and smoky quartz to thousands of carats. Amethyst rare in large sizes, but go to 1000+ carats. Rose quartz, to 30 carats.
Heat Sensitivity No
Luminescence Varies widely due to traces of impurities, usually in the cryptocrystalline varieties. Fluorescent colors include browns, greens, white, orange (LW, SW). Some material shows phosphorescence. X-rays produce faint blue glow in rose quartz. Most varieties inert. Amethyst, inert to weak blue in SW. Aventurine, inert to weak, grayish green or reddish, LW and SW. Rose quartz, inert to weak, purple, SW only.
Luminescence Present Yes
Luminescence Type Fluorescent, Phosphorescent, UV-Long, UV-Short, X-ray Colors
Enhancements Irradiation (occasional), dyeing (common), heat treatment for colored varieties only (occasional), coating (occasional), quench crackling for iridescence (occasional, weakens stone).
Typical Treatments Dyeing, Heat Treatment, Irradiation, Surface Coating
Special Care Instructions None
Transparency Transparent to Opaque
Absorption Spectrum Most varieties, none. Aventurine, broad bands at 648 and 682 nm, other lines may be present. Blue synthetic quartz, distinct bands at 640 and 650, weaker bands at 490, 500, 550 nm.
Phenomena Asterism, chatoyancy, iridescence; Tyndall scattering (rose quartz); aventurescence (quartzite).
Birthstone Amethyst (March, modern); sardonyx (August, traditional); citrine (November, modern).
Formula

SiO2

Pleochroism

Amethyst, weak to moderate, purple and reddish purple. Citrine, very weak, different shades of yellow or orange. Dumortierite quartz, strong blue/violet. Rock crystal and aggregates, none. Rose quartz, weak to strong, different shades of pink. Smoky quartz, dark stones, weak brown/reddish brown. Light stones, weak, light and darker yellowish brown.

Optics

= 1.544; = 1.553 (very constant). Uniaxial (+).

Optic Sign Uniaxial +

Comments by Don Clark, CSM IMG

Quartz is one of the most common minerals on earth. (See The X Factor.) It is well loved as amethyst, citrine, rose, and smoky quartz. There are many other natural varieties, plus synthetic quartz that comes in every color of the rainbow.

Rock crystal, colorless quartz, is rarely used as a gem. However, it is prized by carvers and frequently used as caps for triplets.

Amethyst

Amethyst

Amethyst ranges from a light, pinkish violet to an opaque purple. The lightest shades are called “Rose de France.” While currently out of vogue, they have traditionally been very fashionable. Today, the variety most in demand is “Siberian.” That does not refer to its origin, but to dark purple coloring, with flashes of red or blue.

Citrine

Citrine

Citrine is the yellow to orange variety of quartz. These are the colors traditionally associated with topaz, and they are still confused by many. Its color ranges from a light lemon yellow, to a rich orange. “Madeira” citrine is a strong orange color, with red flashes. It is created by heat treating citrine with the proper iron content and demands the highest price.

Relatively new on the market is ametrine, with zones of both purple and yellow. The colors only reach a medium level of saturation and are never very dark. Cutting the material so both color show is sometimes a challenge for the lapidary. However, a well cut, bi-colored gem is a real delight. Ametrine is only found in Bolivia.

Smokey Quartz

Smokey Quartz

Smoky quartz is also mistaken for topaz. It comes in every shade of brown, from a light tan to nearly black. “Chocolate citrine” is a pleasant brownish/yellow color. Smoky quartz is known for its large sizes. The person who wants a really big gem, without a really big budget, often ends up with one of these.

Rutilated Quartz

Rutilated Quartz

Rose quartz receives its coloring fromfibrous inclusions of a mineral similar to dumortierite. It is always a light to medium pink, but sometimes is influenced by amethyst and picks up a violet shade. Until the 1980s, when a new deposit was discovered in Madagascar, it was never found completely transparent. Indeed, one of its best uses is for star cabs and spheres.

Tyndall scattering is one of the rarest phenomena in gemology, but it is relatively common in Madagascar rose quartz. Tyndall scattering is where light is dispersed by fine particles and produces a blue color. This is the same as what happens when sunlight hits dust particles in the air and why the is sky blue. In rose quartz, you see both pink and blue in the same tone.

While these are the most common varieties, they in no way exhaust the range of crystalline quartz. With the addition of inclusions, the list is nearly endless. In addition, there are stars and cats eye gems in this rich family of gemstones.

Optics

o= 1.544; e= 1.553 (very constant). Uniaxial (+).

Comments by Dr. Joel Arem

Crystalline Quartz

Crystalline quartz is separated here from cryptocrystalline or microcrystalline quartz. The crystalline varieties are those that occur in distinct, visible crystals: amethyst, smoky quartz, citrine, rose quartz, and milky quartz. The color origins in crystalline quartz are complex and are only now beginning to be fully understood.

The stable form of quartz below a temperature of 573°C is known as a-quartz. Between 573° and 870° another silica mineral, tridymite, forms. At 1470°, tridymite undergoes a structural rearrangement, resulting in the appearance of a new silica type called cristobalite, which is isometric. Finally, at 1710°, cristobalite melts to an extremely viscous liquid. If this liquid is chilled quickly, a glass forms (silica glass) that has many useful properties but no regular internal structure.

Cristobalite has no gem significance but appears in some types of volcanic glass as white globules and crystals resembling snowflakes. These form as a result of rapid cooling from high temperature.

The colored, crystalline quartz varieties generally occur in pegmatitcs and veins, having been deposited from water solutions over a long period of time. As a result of slow crystal growth, many such crystals achieve great internal perfection and yield enormous pieces of faceting rough. The only color varieties that do not form such large crystals are amethyst and rose quartz.

Cryptocrystalline Quartz

Cryptocrystalline quartz varieties are colored chiefly by mineral impurities in the growth environment, including oxides of Fe, Mn, Ti, Cr, Ni, and other elements. They form either as gelatinous masses that slowly dehydrate and crystallize or by deposition from slowly percolating ground waters, depositing silica over a long period of time. This latter type of deposition results in banding that is seen in certain types of agate. Deposition within a spherical cavity, such as a gas pocket in basalt or other volcanic rock, results in concentric banding also seen in agates.

Cryptocrystalline quartz varieties offer a huge diversity of patterns and colors. The most generally widespread of these materials is composed of tiny fibers of silica and is known as chalcedony. Names within the cryptocrystalline quartz family are generally based on colors and patterns. The solid-colored materials are mostly chalcedony stained by oxides and are referred to as jaspers. Banded varieties, or materials with moss-like inclusions, are known as agate.

Patterned Chalcedony

Stone Sizes

Names

The name quartz comes from the Greek, “krystallos,” meaning ice. Amethyst also comes from a Greek word. “Amethystos,” meaning “not drunk.” It was believed one could drink all night and remain sober if they had an amethyst in their mouth. Citrine is from the French, “citrin,” meaning yellow.

Quartz is an unusual mineral. It is stable below 573 degrees Centigrade, but between 573 and 870 degrees, tridymite, (another silica mineral,) forms. At 1470 degrees, tridymite undergoes a structural rearrangement and becomes cristobalite, which is isometric. At 1710 degrees, cristobalite melts to a viscous liquid. If cooled quickly, it forms silica glass with no internal structure.

Tridymite and cristobalite have no gem significance; except that the “snowflakes” sometimes found in obsidian are cristobalite.

Quartz grows in primarily in pegmatites, but is hydrothermal grown in laboratories. Quartz grows very large, with cut gems in the thousands of carats. The exceptions are amethyst, which rarely produces a clean gem of 100 carats, and rose quartz, which rarely exceeds 30 carats in a transparent gem. Translucent specimens can weigh several pounds.

Quartz is one of the first gems to be synthetically grown on a large scale. Major development was done during World War II, to supply crystals for radios. Today, our computer industry is based on synthetic quartz. Not that there is a shortage of natural crystals, but the synthetics are always clean and are less time consuming to trim into the necessary pieces.

Rock crystal is from the Greek krystallos, meaning ice, because the Greeks thought it was ice frozen forever hard by an unnatural frost created by the gods. Amethyst comes from the Greek amethystos, as mentioned. Citrine is in allusion to the color citron (yellow). Chalcedony is an ancient name, perhaps from Chalcedon, a seaport in Asia Minor. Agate is from the Greek achate, the name of a river in southwestern Sicily where the material was found. Onyx is from the Greek word for nail or claw. Sard is from Sardis, the ancient locality reputed to be the origin of the stone. Carnelian is from the Latin carnis (flesh), in allusion to the red color. Plasma is from the Greek for something molded or imitated because it was used for making intaglios. Prase is from the Greek prason, meaning leek, in allusion to the color. Heliotrope is from Greek words helios (sun) and tropein (turn) because according to Pliny, it gives a red reflection when turned to face the sun while immersed in water. Flint and chert are of uncertain origin.

Enhancements

Identifying Characteristics

Natural quartz, Color zoning, twinning, liquid, 2 and 3 phase inclusions, negative crystals, zebra stripes. May show bull’s-eye or Airy’s spiral.

Synthetic quartz is identified “breadcrumbs” or by a lack of natural inclusions. May also show 2-phase spicule inclusions or a seed. Cobalt blue, greenish yellow and grayish green, not found in nature.

Polariscope testing is no longer relevant, as some synthetics now duplicate natural twinning.

Variety and Trade Names

 

Misnomers

by Joel E. Arem, Ph.D., FGA, Donald Clark, CSM IMG, Barbara Smigel, PhD. GG

Enter your email to access the Ultimate Opal Buying Guide for free!

FREE

THANK YOU!

 

PLEASE CHECK YOUR EMAIL FOR THE E-BOOK

Follow us on Facebook