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