Conchoidal, Conchoidal, Gemstones of the world (2001)
Conchoidal, Conchoidal, Gemstones of the world (2001) More from other references
SiO 2 · nH 2OWalter Schumann , Gemstones of the world (2001) More from other references
SiO 2 · nH 2OGemdat.org , Management Team (2012)