Turquoise is a mineral with a hardness of 6 out of 10 on the Mohs scale of mineral hardness [?]. These Triclinicly structured gems are made of hydrated copper aluminum phosphate, their full chemical compound being Cu|Al6(PO4)4(OH)8,5H2O.

Turquoise is a hydrated phosphate of copper and aluminum in the Phosphates, Arsenates, Vanadates group, with a triclinic crystal system.

It rarely occurs as prismatic crystals. It is usually found as light-blue or green masses, nodules, and veins, sometimes filling cavities in various rocks. When it occurs as thin strips, it is tighter and brightly-colored at the center, lighter and porous on the outside.

It is light, very fragile, with good cleavage that is parallel to its prism faces, and fracture that is smoothly-curved, like that of a shell. It is translucent only in thin sections, with a luster that may be like wax, or porcelain. Its hardness corresponds to the size of turquoise grains in the crystalline aggregate, progressing from semi-hard to a consistency almost like blackboard chalk. It has a very high melting point, and is soluble in hydrochloric acid only when heated. It is also sensitive to soap, water, and grease.

When polished, untreated turquoise may be a strong blue color, but is more often pale sky blue, greenish blue or pale green.

As a mineral mass, turquoise can contain narrow veins of other material, either isolated or like a connected web; these are usually black or brown, sometimes yellowish brown. It may also contain whitish patches of foreign materials, or even tiny crystals of pyrite.

Turquoise is a secondary mineral resulting from the alteration of aluminum-bearing rocks rich in apatite and chalcopyrite, together with chalcedony and "limonite."

Exceptional sky-blue turquoise, sometimes with white markings, have been found in Iran (Kuh-i-Nishapur, Neyshabur), Egypt (Sinai peninsula) and Turkestan (Samarkand). It is also found in Australia (Queensland, Victoria, and New South Wales). Turquoise from Los Cerillos, New Mexico, and Nevada (USA) is also well-regarded, though it is less popular because it is more greenish than blue.

The best quality turquoise still comes from Iran, but no longer in large amounts. Recent deposits in the USA (Nevada, California, Arizona, New Mexico) have been increasingly exploited. Even if most of it is of low quality, it is used after being treated to improve its hardness, consistency, and color. This treatments include: Impregnation with paraffin or wax, or impregnation with colorless or colored plastic, to make the color livelier, eliminate porosity, and make material of low hardness easier to polish.

The specific gravity [?] for Turquoise is 2.8, it's refractive index [?] is 1.61-1.65, and it's double refraction [?] is 0.04.

History

Turquoise derives its name from the French word, "pierre turquoise," meaning "Turkish stone," from the fact that it was brought to Europe from the Eastern Mediterranean by Levantine traders, generally known as Turks. It has been mined in Iran since ancient times. The Aztecs extracted it in the area that is now New Mexico. It has served as an ornament for a very long time, having been used by the Egyptians for some thousands of years B.C. But they too, imitated turquoise with ceramic material.

Industrial Usages

Turquoise is a very valuable ornamental stone. Specimens that are of lower quality are often colored artificially or "improved" with oil, wax, or plastics, which are sometimes difficult to tell from untreated high-quality stones. But when examined under a lens, the permeation of paraffin appears as small, white, opaque patches side by side with bluer, translucent areas, sometimes set against a faint background of larger indented patches.


Because of this it has become one of the most controversial gems, as much of the material being sold today has been given so many different treatments that it is completely altered from its original appearance. Imitations now outnumber genuine turquoise.


Its attractive color and physical features are usually imitated using other similarly-colored materials like non-clay ceramic material, marble, plastic, and nodules of other minerals like magnesite and howlite, that have been externally stained. Even similarly-hued natural minerals like chrysocolla and lazulite are employed as turquoise imitations.


Synthetic turquoise has also been produced, which has its own unique honeycomb structure visible under a simple lens.


But what does turquoise look like when it has not been interfered with in any way? Its surface has a uniform texture like that of unglazed china or rock that is very fine-grained.


Untreated turquoise is used almost rough, in lightly polished nodules, or more often, in the form of rounded, polished stones that are pierced for necklaces or other items of jewelry. It is also made into carved gems, cabochons, or mini-sculptures.


Like all gems which are in pastel shades, the richer-colored types are the most preferred. The favored turquoise hue is the strong sky blue, the pale greenish blue being less preferred, and the paler green even less so. Because it has a wide range of hardness, the hardest types are worth the most.


Being regularly in demand, genuine turquoise is quite highly prized in relation to other opaque gems, even if there are a lot of it on the market. Its value is exceeded only by lapis lazuli and top quality jadeite jade.

You May Also Like...

Howlite

Howlite: Howlite an opaque, massive mineral used for ornamental and utilitarian articles. is a rarity for collectors It has a monoclinic tabular crystal system with a subvitreous luster. The most common occurrence is in the form of a cauliflower. Howlite is found in borate deposits, with most ornamental pieces found from various sites in California (USA) and Mexico. It occurs as opaque white, and may be (read full)

Smithsonite

Smithsonite: Smithsonite is a mineral in the group of Nitrates, Carbonates, Borates, with a hexagonal crystal system. It appears uncommonly in rhombohedral or scalenohedral crystals. But most of the time it appears with curved faces, like a thick creamy aqua-green mixture poured on rock and left to aggregate in clusters shaped like bunches of grapes, rounded, kidney-like, or to form like elegant icicles, and (read full)

Jet Lignite

Jet Lignite: Jet is an organic gem material composed of lignite, and is a bituminous coal which can be polished. It is compact, homogeneous, has a hard, glossy surface and black interior variety of fossilized lignite or coal. It is an opaque black coalified fossilized drift wood from the coniferlike, 180 million years old 'Araucaria' or monkey puzzle tree that has been dried and fractured following death of (read full)

Serpentine

Serpentine: Serpentine may refer to a single mineral but more often to a group of minerals including antigorite, chrysotile, clinochrysotile, and lizardite, which are altered products of basic and ultra-basic rocks. Rock composed of these minerals is called serpentinite. It comes in all the hues of green.
In mineralogy, serpentine is divided into three polymorphs, crystals with the same chemical substanc (read full)

Tags

Terms

Double Refraction or dr is the ability of a mineral to separate a refracted ray of light into 2 rays. If held over an image or text it will display the object 2x its original size.

Mohs Scale of Mineral Hardness is the standard used to categorize a mineral's ability to resist scratching. It gets its name from Friedrich Mohs, the German geologist who first created the scale.

RI or Refractive Index defines light's ability to move through the mineral or in a general sense, any material.

SG or Specific Gravity is the ratio of the weight of any substance to that of pure water at temperature of 3.98°C(39.2°F) and standard atmospheric pressure. This is important to note when actively seeking these minerals in the wild. Minerals with a higher SG will settle below material with a lower sg over time.