Turquoise
Current inventory:  0 gems
 

  
Turquoise gets its name rom the French word turquoise meaning Turkish. Turquoise from the southern slopes of the Al-Mirsah-Kuh Mountains in Iran was originally brought to Europe through Turkey.

Discovered in Prehistory;   IMA status:  Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

CuAl₆(PO₄)₄(OH)₈·4(H₂O)

Hydrated Copper Aluminum Phosphate

Molecular Weight:

813.44 gm

Composition:

Aluminum

19.90 %

Al

37.60 %

Al₂O₃

Copper

7.81 %

Cu

9.78 %

CuO

Phosphorus

15.23 %

P

34.90 %

P₂O₅

Hydrogen

1.98 %

H

17.72 %

H₂O

Oxygen

55.07 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Phosphates

Strunz 8th Ed. ID:

7/D.15-40

Nickel-Strunz 10th Ed. ID:

8.DD.10

8 : PHOSPHATES, ARSENATES, VANADATES
D : Phosphates, etc. with additional anions, with H₂O
D : With only medium-sized cations, (OH, etc.):RO₄= 2:1

Related to:

Turquoise Group. Chalcosiderite - Turquoise Series. Planerite - Turquoise Series. The copper analogue of Faustite. Isostructural with Chalcosiderite.

Members of Group:

Turquoise Group: Aheylite, Chalcosiderite, Faustite, Planerite, Turquoise

Varieties:

Agaphite, Rashleighite

Synonyms:

Calaite, Callaica, Callaina, Callais (of Pliny), Chalchihuitl (of Blake), Chalchite, Chalchuite, Forizego, Hydrargillite (of Hausmann), Johnite, Oriental Turquoise, Turques, Turquois

Crystal Data

Crystallography:

Triclinic - Pinacoidal

Crystal Habit:

Rare steep pinacoidal crystals, to 3 mm; fine granular to cryptocrystalline, nodular to globular crusts, veinlets, massive. Often found as pseudomorphs after orthoclase; also after apatite, bone and teeth.

Twinning:

None

Physical Properties

Cleavage:

[001] Perfect, [010] Good

Fracture:

Conchoidal to Smooth

Tenacity:

Brittle

Moh's Hardness:

5.0 - 6.0

Density:

2.60 - 2.86 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Blue, Blue Green, Green, Green Gray, light Blue

Transparency:

Transparent, Sub-Translucent to Opaque

Luster:

Vitreous in crystals, Waxy to Dull in massive varieties

Refractive Index:

1.610 - 1.650  Biaxial  ( + )

Birefringence:

0.0400

Dispersion:

Relatively Strong; r < v

Pleochroism:

Weak; X = colorless, Z = pale blue or pale green

Other:

Soluble with difficulty in HCl.

Occurances

Geological Setting:

A secondary mineral formed in the potassic alteration zone of hydrothermal porphyry copper deposits; a vein-filling in volcanic rocks and phosphate-rich sediments.

Common Associations:

Allophane, Kaolinite, Montmorillonite, Pyrite, Wavellite

Common Impurities:

Fe, Ca

Type Locality:

None; Prehistoric

Year Discovered:

Prehistoric

View mineral photos:

Turquoise Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Turquoise is typically opaque and available as massive material that is commonly used for cabochons, beads and carvings. The name Turquoise is synonamous with the name of the color of the material. It is found in various shades of blue, blue-green and green. It may be a solid color or veined with black or brown matrix and referred to as Spiderweb Turquoise. Turquoise is commonly simulated by other materials, both natural and artificial, that are often difficult to tell from the real thing. Turquoise may also be treated to improve color. Turquoise is possibly to most popular non-transparent mineral in the jewelry trade. It has been in use as a valuable gem since at least 6000 BC when it was mined by early Egyptians. It has been used as a cultural, religious and ornamental gem by many cultures throughout history and is still very popular today.

There are many locations for good Turquoise specimens including Ma’dan, 45 km northwest of Neyshabur, Iran; Katonto, north of Kolwezi, Katanga Province, Congo (Shaba Province, Zaire); and Greenlee and Gila Counties, Arizona, USA.
 

  
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