Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Conchoidal, Brittle
Conchoidal, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle
Zn 4Si 2O 7(OH) 2H 2OMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references
SiCArthur Thomas , Gemstones (2009)