Uneven, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001)
Gems, Sixth Edition (2006), Gems, Sixth Edition (2006)
(Ca,Mn2+ ,Fe2+ ) 3Al 2BSi 4O 15(OH)Anthony et al , Handbook of mineralogy (2001)
SiO 2Michael OâDonoghue , Gems, Sixth Edition (2006)