USA, Southern and central Africa, green, blue, China, India, USA, Italy, green, blue, China, India, USA, Italy
Southern and central Africa
Uneven, Uneven, Gemstones of the world (2001) More from other references
Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
H 4Mg 3Si 2O 9Walter Schumann , Gemstones of the world (2001) More from other references
Al 2SiO 5Arthur Thomas , Gemstones (2009)