Brittle, Uneven
UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
Mn2+5(PO 4) 2(PO 3OH) 2 · 4H 2O)Michael OâDonoghue , Gems, Sixth Edition (2006)
Ca 2(Mg,Al) 6(Si,Al,B) 6O 20Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references