UnevenArthur Thomas, Gemstones (2009) Tough, UnevenArthur Thomas, Gemstones (2009) Tough, Brittle, Uneven
UnevenWalter Schumann, Gemstones of the world (2001) More from other references, UnevenWalter Schumann, Gemstones of the world (2001) More from other references, Uneven
Mn 8Si 6O 15(OH,Cl) 10Ulrich Henn and Claudio C.
(Zn,Fe)SMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references