Granular
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), Uneven
Ca 2(Mg,Fe)Al 2(SiO 4)(Si 2O 7)(OH) 2 · H 2O)Arthur Thomas , Gemstones (2009)
(Mn2+ ,Fe2+ ,Mg,Ca) 2(PO 4)(F,OH)Michael OâDonoghue , Gems, Sixth Edition (2006)