Conchoidal, ConchoidalArthur Thomas, Gemstones (2009)
Brittle, UnevenArthur Thomas, Gemstones (2009), Brittle, Uneven
K(Ca,Na) 2Si 4O 10(OH,F) · H 2OMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references
(Mg,Fe)Al 3(BO 4)(SiO 4)OUlrich Henn and Claudio C.