Fibrous, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), Uneven
AlAl6O3BSi3O18
(Al,Mg) 8(Al,Si) 6O 20Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references