Milarite
Milarite is a very rare gem. Crystals are colorless, pale green, yellowish green and yellowish. Most crystals are not facetable but occasional very small gemmy crystals are found. There are very few sources for Milarite crystals. These include St. Gotthard, Switzerland; Minas Gerais, Southeast Region, Brazil; Guanajuato, Mexico; Fujian Province, China; Arandis, Swakopmund District, Erongo Region, Namibia and Albany, Carrol County, New Hampshire, USA.
| Category: | Osumilite Group |
| Formula: | K2Ca4Al2Be4Si24O60 · H2O |
| Crystallography: | Hexagonal – Dihexagonal Dipyramidal |
| Crystal Habit: | Typically as well-formed hexagonal prisms, to 4 cm; as radial-fibrous aggregates and intergrowths. |
| Twinning: | None |
| Cleavage: | [0001] Imperfect, [1120] Imperfect |
| Fracture: | Conchoidal to Uneven |
| Tenacity: | Brittle |
| Hardness (Mohs): | 5.5 – 6.0 |
| Density: | 2.46 – 2.61 (g/cm3) |
| Luminescence: | Some specimens may be fluorescent |
| Radioactivity: | Barely Detectable; GRapi = 56.71 (Gamma Ray American Petroleum Institute Units) |
| Color: | Colorless, White, Greenish White, Yellowish White |
| Transparency: | Transparent to Translucent, Opaque |
| Luster: | Vitreous |
| Refractive Index: | 1.532 – 1.548 Uniaxial ( – ); anomalously Biaxial, sectored, with a Uniaxial core |
| Birefringence: | 0.0030 – 0.0160 |
| Dispersion: | n/a |
| Pleochroism: | n/a |
