Handbook of mineralogy (2001), Difficult, Fibrous
Conchoidal, Brittle, Metallic, Conchoidal, Handbook of mineralogy (2001)
Ca 6Si 6O 17(OH) 2Michael OâDonoghue , Gems, Sixth Edition (2006)
(Mg,Fe2+ ) 3Si 2O 5(OH) 4Anthony et al , Handbook of mineralogy (2001)