ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001), Brittle, Metallic
Conchoidal, Conchoidal, Gemstones of the world (2001) More from other references
BeAlSiO 4(OH)Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
SiO 2 · nH 2OGemdat.org , Management Team (2012)