Turquoise
Opaque, blue-to-green mineral / From Wikipedia, the free encyclopedia
Dear Wikiwand AI, let's keep it short by simply answering these key questions:
Can you list the top facts and stats about turquoise?
Summarize this article for a 10 year old
SHOW ALL QUESTIONS
This article is about the mineral. For the color, see Turquoise (color). For other uses, see Turquoise (disambiguation).
Turquoise is an opaque, blue-to-green mineral that is a hydrous phosphate of copper and aluminium, with the chemical formula CuAl6(PO4)4(OH)8·4H2O. It is rare and valuable in finer grades and has been prized as a gemstone for millennia due to its hue.
This article needs additional citations for verification. (June 2022) |
Quick Facts General, Category ...
Turquoise | |
---|---|
General | |
Category | Phosphate minerals |
Formula (repeating unit) | CuAl6(PO4)4(OH)8·4H2O |
IMA symbol | Tqu[1] |
Strunz classification | 8.DD.15 |
Crystal system | Triclinic |
Crystal class | Pinacoidal (1) (same H–M symbol) |
Identification | |
Colour | Turquoise, blue, blue-green, green |
Crystal habit | Massive, nodular |
Cleavage | Perfect on {001}, good on {010}, but cleavage rarely seen |
Fracture | Conchoidal |
Mohs scale hardness | 5–6 |
Luster | Waxy to subvitreous |
Streak | Bluish white |
Diaphaneity | Opaque |
Specific gravity | 2.6–2.9 |
Optical properties | Biaxial (+) |
Refractive index | nα = 1.610 nβ = 1.615 nγ = 1.650 |
Birefringence | +0.040 |
Pleochroism | Weak |
Fusibility | Fusible in heated HCl |
Solubility | Soluble in HCl |
References | [2][3][4] |
Close
Like most other opaque gems, turquoise has been devalued by the introduction of treatments, imitations, and synthetics into the market. The robin egg blue or sky blue color of the Persian turquoise mined near the modern city of Nishapur, Iran, has been used as a guiding reference for evaluating turquoise quality.[5]