Gemstones (2009)
Uneven, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle, Conchoidal
Al 2SiO 5Arthur Thomas , Gemstones (2009) More from other references
(Ca,Na)(Mg,Fe,Al,Ti)(Si,Al) 2O 6Anthony et al , Handbook of mineralogy (2001)