Uneven, Conchoidal, UnevenWalter Schumann, Gemstones of the world (2001)
Sub-Conchoidal, Irregular/uneven, Sub-Conchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
Perfect {010}, imperfect {100}
[100] Perfect, [110] Good, [011] Distinct
Ca2Al3(SiO4)3(OH)
(Li,Na)Al(PO 4)(F,OH)Michael OâDonoghue , Gems, Sixth edition (2006) More from other references