Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001)
Irregular/uneven, Brittle, Metallic
Na(Li 1.5Al 1.5)Al 6(Si 6O 18)(BO 3) 3(OH) 3(OH)Gemdat.org , Management Team (2012) Formula given for elbaite.
Ca6(Al,Si)2(SO4)2B(OH)4(OH,O)12•26(H2O)