Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Brittle, Uneven
Conchoidal, ConchoidalAnthony et al, Conchoidal, Brittle, Conchoidal
ThCa 2Si 8O 20Walter Schumann , Gemstones of the world (2001) More from other references
(Zn,Cu)Al 6(PO 4) 4(OH) 8 · 4H 2OMichael OâDonoghue , Gems, Sixth Edition (2006)