ConchoidalWalter Schumann, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Brittle, Metallic
Conchoidal, Conchoidal, Gemstones of the world (2001) More from other references
Be 2BO 3(OH)Ulrich Henn and Claudio C.
SiO 2 · nH 2OGemdat.org , Management Team (2012)