Turquoise
A copper phosphate the colour of dry-country sky, worn from Egypt to Arizona.
- Family
- Turquoise
- Formula
- CuAl₆(PO₄)₄(OH)₈·4H₂O
- Mohs
- 5 to 6
- System
- Triclinic
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Science
Turquoise forms in arid regions where copper-bearing water percolates through aluminium-rich rock. Copper makes it blue; iron shifts it green. It is porous and reacts with skin oils, which is why old pieces darken. Its host rock left inside the stone is the 'matrix' or spiderweb.
- Mineral
- Turquoise
- Formula
- CuAl₆(PO₄)₄(OH)₈·4H₂O
- Crystal system
- Triclinic
- Mohs hardness
- 5 to 6
- Specific gravity
- 2.60 to 2.90
- Refractive index
- 1.610 to 1.650
- Lustre
- Waxy
- Colours
- Sky blue, Blue-green, Green
- Birthstone
- December
Composition
CuAl₆(PO₄)₄(OH)₈·4H₂O. Made of Copper, Aluminium, Phosphorus, Oxygen, Hydrogen, with trace Iron responsible for colour.
Origin
- IranNishapur, historic finest
- United StatesArizona, Nevada, New Mexico
- ChinaHubei
- Mexico
- EgyptSinai, historic
Filled dots are primary sources
Rarity
Untreated, hard, evenly coloured turquoise is now rare; most is stabilised with resin, and much is dyed howlite or reconstituted powder.
- 1 Abundant
- 2 Common
- 3 Uncommon
- 4 Rare
- 5 Exceptional
Hardness
Turquoise sits at 5 to 6 on the Mohs scale. Glass and a knife blade are about as hard; it wears well with care.
Energy
Associations from crystal-healing tradition, recorded here as folklore. They are not medical claims.
Chakras
- Throat
Element
- Water
Zodiac
- Sagittarius
- Scorpio
- Pisces
Planets
- Jupiter
- Venus
Properties
- Protection
- Healing
- Friendship
- Clear speech
- Travel
Lore
Egyptians mined it in the Sinai from about 3000 BCE; Aztecs made mosaics and masks of it; Persian kings wore it against violent death. The name is French, 'Turkish', because it reached Europe through Turkey.
In the American Southwest it is sacred to Navajo, Zuni and Pueblo peoples, and Navajo silverwork since the 1880s made it the region's emblem.
- Sleeping BeautyThe Arizona mine famous for clean blue, closed in 2012.
- TreatmentStabilisation with resin is standard; disclosure matters.