Conchoidal, Conchoidal, Gemstones of the world (2001) More from other references
Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Brittle, Metallic
SiO 2 · nH 2OGemdat.org , Management Team (2012)
CuSMichael OâDonoghue , Gems, Sixth edition (2006) More from other references