Uneven, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle, Conchoidal
Brittle, UnevenArthur Thomas, Gemstones (2009), Brittle, Uneven
Na(Fe2+3)Al 6(Si 6O 18)(BO 3) 3(OH) 3(OH)Gemdat.org , Management Team (2012)
(Mg,Fe)Al 3(BO 4)(SiO 4)OUlrich Henn and Claudio C.