Tinzenite
Tinzenite is a rare boron silicate mineral that is rarely available as a faceted gem. Tinzenite is a member of the Axinite Group of minerals that also includes Axinite-(Fe), Axinite-(Mg) and Axinite-(Mn). Tinzenite‘s bright orange color makes for very attractive mineral specimens or faceted gems. Gems are suitable for jewelry with a Mohs hardness of 6.5 – 7.0.
Distribution: From near Tinzen, in the Val d’Err, Graubünden, Switzerland. In the Cassagna and Gambatesa mines, Val Graveglia, near Chiavari, Liguria, Italy. From Akatore, New Zealand.
| Chemical Formula: | (Ca,Mn2+,Fe2+)3Al2BSi4O15(OH) |
| Calcium Manganese Iron Aluminum Boron Silicate Hydroxide | |
| Molecular Weight: | 572.45 gm |
| Composition: | Calcium | 12.60 % | Ca | 17.63 % | CaO |
| Manganese | 8.64 % | Mn | 11.15 % | MnO | |
| Aluminum | 9.43 % | Al | 17.81 % | Al2O3 | |
| Iron | 2.93 % | Fe | 3.77 % | FeO | |
| Silicon | 19.63 % | Si | 41.98 % | SiO2 | |
| Boron | 1.89 % | B | 6.08 % | B2O3 | |
| Hydrogen | 0.18 % | H | 1.57 % | H2O | |
| Oxygen | 44.72 % | O | |||
| 100.00 % | 100.00 % | = TOTAL OXIDE |
| Crystallography: | Triclinic – Pinacoidal |
| Crystal Habit: | As aggregates of prismatic crystals, to 5 mm; massive. |
| Twinning: | None |
| Cleavage: | Good on {100}; Poor on {001}, {110}, {011} (by analogy to the Axinite Group). |
| Fracture: | Irregular/Uneven to Conchoidal |
| Tenacity: | Brittle |
| Moh’s Hardness: | 6.5 – 7.0 |
| Density: | 3.355 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioactive |
| Color: | Yellow, Brownish Yellow-Green, Orange, Red; Orange to Red in thin section |
| Transparency: | Transparent to Subtranslucent |
| Luster: | Vitreous |
| Refractive Index: | 1.690 – 1.705 Biaxial ( – ) |
| Birefringence: | 0.0110 |
| Dispersion: | Weak to Distinct |
| Pleochroism: | In thick sections, weak; X = light brown; Y = violet; Z = light yellow or colorless |
