Conchoidal, ConchoidalArthur Thomas, Gemstones (2009)
Uneven, Brittle, Metallic, Gemstones (2009)
(Ca,Fe,Mn,Mg) 3Al 2BSi 4O 15(OH)Walter Schumann , Gemstones of the world (2001) More from other references
Na 2[Al 2Si 3O 10] · 2H 2OMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references