Triphylite
Triphylite is a rare phosphate mineral that forms a solid solution series with the mineral Lithiophilite which it is often associated with. Lithiophilite is rich in manganese whereas Triphylite is rich in iron. The series is often called the Triphylite Series and the two minerals are often listed together in mineral references. Triphylite’s name in Greek means “family of three” referring to its three ions: lithium, iron, and manganese. Gems cut from Brazilian crystals can be dichroic changing from shades of reddish brown to shades of green. Both colors may vary widely. The reds may be brick red to brownish red, the greens from brownish green to green.
Triphylite occurs in numerous localities worldwide but gemmy crystals are only found at a few locations including Minas Gerais, Brazil and North Groton, Grafton County, New Hampshire, USA.
| Category: | Phosphate minerals |
| Formula: | LiFe2+PO4 |
| lithium iron(II) phosphate mineral | |
| Crystallography: | Orthorhombic – Dipyramidal |
| Crystal Habit: | Crystals rare, typically prismatic, several other forms. Commonly subhedral, to 6.5 m, cleavable, compact, massive. |
| Twinning: | None |
| Cleavage: | [100] nearly Perfect, [010] Imperfect, [011] Interrupted |
| Fracture: | Irregular/Uneven to Sub-Conchoidal |
| Tenacity: | Brittle |
| Hardness (Mohs): | 4.0 – 5.0 |
| Density: | 3.50 – 3.58 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioactive |
| Other: | Soluble in acids. |
| Color: | Brownish Green, Greenish Gray, Bluish Gray, Brownish to Black where altered |
| Transparency: | Transparent to Translucent |
| Luster: | Vitreous, Resinous to Subresinous |
| Refractive Index: | 1.675 – 1.702 Biaxial ( +/- ) |
| Birefringence: | 0.0060 – 0.0080 |
| Dispersion: | Strong; r < v |
| Pleochroism: | Very Weak; some Lithiophilites may show deep reddish brown/green |
