Turquoise
Phosphate · CuAl₆(PO₄)₄(OH)₈·4H₂O
Turquoise is a blue-to-green copper aluminium phosphate, one of the oldest gemstones, usually found as opaque veins and nodules.
What is turquoise?
Turquoise is a hydrated copper aluminium phosphate valued as a gem for thousands of years. It is almost always massive rather than crystalline, in sky-blue to green, often veined with brown or black “matrix” from the host rock. Its colour comes from copper (blue) and iron (green).
Properties
- Chemical formula
- CuAl₆(PO₄)₄(OH)₈·4H₂O
- Category
- Phosphate
- Hardness (Mohs)
- 5–6
- Crystal system
- Triclinic
- Lustre
- Waxy to dull
- Streak
- Pale blue-green to white
- Colour
- Sky-blue to green
- Cleavage / fracture
- Usually not seen (massive)
How to identify turquoise
- →Opaque sky-blue to green, often with a dark veined matrix.
- →Waxy to dull lustre; massive, not crystalline.
- →Hardness 5–6; pale blue-green streak.
- →Porous, so it can absorb oils and change colour over time.
Where turquoise is found
Historic turquoise comes from Iran (Nishapur), the southwestern USA (Arizona, Nevada) and China.
Turquoise finds on minShelf
No turquoise on the map yet.
Have one? Be the first to add it.
Think you've found turquoise?
Photograph it and minShelf takes a first guess at what it is, records its properties, and pins it on your map. Other collectors help confirm the identification. Free.