Turquoise

Turquoise is a mineral used as a gemstone in jewelry. It has a distinctive greenish-blue color with some lighter and darker variations. It was used long ago by the Egyptians and the Aztecs, who believed turquoise had protective powers, and it is found in Native American jewelry.

It is a copper aluminum phosphate with the chemical composition: CuAl₆(PO₄)₄(OH)₈·4H₂O. It has a hardness rating of 5 - 6 on the Mohs scale, and a specific Gravity of around 2.6 - 2.8.

Turquoise is the birthstone for December

References

• http://www.gemstone.org/gem-by-gem/english/turquoise.html
• http://www.galleries.com/minerals/phosphat/turquois/turquois.htm
• http://minerals.usgs.gov/minerals/pubs/commodity/gemstones/sp14-95/turquoise.html