ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001)
UnevenAnthony et al, Handbook of mineralogy (2001), UnevenAnthony et al, Handbook of mineralogy (2001)
SiO 2Ulrich Henn and Claudio C.
Na(Mn2+ ,Ca) 2Si 3O 8(OH)Michael OâDonoghue , Gems, Sixth Edition (2006)