ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), Uneven
ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001)
Zn 2(Fe2+ ,Mn2+ )(PO 4) 2 · 4H 2OMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references
SiO2