Tenacity
-
-
Solubility
-
-
Durability
-
-
Specific Gravity
3.03-3.185.2
1
7.18
👆🏻
Fracture
Uneven, Irregular, Conchoidal
Subconchoidal, Conchoidal
Cleavage
{???} Indistinct
Good in one direction
Mohs Hardness
7-7.56-6.5
2
10
👆🏻
Chemical Composition
Na(Mg 3)Al 6(Si 6O 18)(BO 3) 3(OH) 3(OH)Gemdat.org , Management Team (2012)
(Fe,Mn)Ta 2O 6Walter Schumann , Gemstones of the world (2001) More from other references