Charoite is a complex silicate mineral. Published chemical compositions are in disagreement. We checked numerous references, and each one presented a different composition. The compositions reported below are from the Glossary of Geology [3], Mineralogical Magazine [4], and Mindat.org [1].(K,Na)5(Ca,Ba,Sr)8Si8O46(OH,F)·nH2O [3](K,Sr,Ba,Mn)15-16(Ca,Na)32[Si70(O,OH)180] (OH,F)4·nH2O [4](K,Sr)15-16(Ca,Na)32[Si6O11(O,OH)6]2 [Si12O18(O,OH)12]2[Si17O25(O,OH)18]2 (OH,F)4·~3H2O [1]
Determining a composition for this mineral might be difficult for two reasons: 1) well-formed crystals and specimens of pure charoite have not been found; and, 2) charoite is always intimately associated with and intergrown with numerous other minerals.
| Physical Properties of Charoite | |
| Chemical Classification | Silicate |
| Color | Purple to violet, light brown. Weathers to chalky white. Color caused by the presence of manganese. |
| Streak | White |
| Luster | Vitreous to pearly to silky |
| Diaphaneity | Semi-translucent to opaque |
| Cleavage | Three directions of cleavage, but rarely seen because of the material’s texture. Breaks with a conchoidal fracture. |
| Mohs Hardness | 5 to 6 |
| Specific Gravity | 2.5 to 2.6 |
| Diagnostic Properties | Purple to violet color; fibrous to swirly color pattern, sometimes chatoyant, almost always impure. |
| Chemical Composition | (K,Na)5(Ca,Ba,Sr)8Si8O46(OH,F) . nH2O |
| Crystal System | Monoclinic |
| Uses | Rocks containing abundant charoite with a pleasing color and interesting pattern are often cut into gems or used as an ornamental stone. |