Almandine (Garnet)
Almandine is a known member of the Garnet Group of minerals that includes Almandine, Andradite, Grossular, Pyrope, Spessartine, and Uvarovite. Almandine is considered the most variety. Almandine always contains some Spessartine and Pyrope elements which create a range that is wide of including brown, red-brown, purplish red, wine red, purple and deep red. Almandine is the iron aluminum garnet. Pure Almandine and Pyrope that is pure are in nature and most specimens are a definite percentage for the two. Silky inclusions may be present in many Almandine gems that is only noticeable under magnification. Nevertheless, material from Idaho, United States Of America and India is recognized to contain inclusions of asbestiform minerals such as pyroxene and amphibole which create a chatoyancy that produces a star that is 4-raid.
Almandine, like other varieties of Garnet, forms rounded crystals with 12 rhombic or 24 faces that are trapezoidal combinations of these and some other types. This practice that is crystal classic for the Garnet Group of minerals.
Distribution: Widespread. Some localities for fine crystals include: in the Zillertal, Tirol, Austria. At Falun, Sweden. In Norway, from near Body. From the Akhmatovsk deposit, near Zlatoust, Ural Mountains, Russia. In the USA, from Roxbury, Litchfield County, and Southbury, New Haven County, Connecticut; at Auburn, Androscoggin County, and Topsham, Sagadahoc County, Maine; from Westfield and Russell, Hampden County, Massachusetts; and at Hanover, Grafton County, brand new Hampshire. From Avondale, Chester County, Pennsylvania; a big deposit that is commercial the Barton mine, North Creek, Warren County, New York; at Michigamme, Marquette County, Michigan; from Salida, Chaffee County, Colorado; and at Ft. Wrangell, Stikine River, Alaska. In Brazil, at Pernambuco, Bahia. From the Miami district, Zimbabwe. At Broken Hill and Thackaringa, brand new South Wales, as well as in the Harts Range, Northern Territory, Australia. From Yamanoo, Ibaragi Prefecture, while the Ishikawa region, Fukushima Prefecture, Japan.
| Chemical Formula: | Fe2+3Al2(SiO4)3 |
| Iron Aluminum Silicate | |
| Molecular Weight: | 497.75 gm |
| Composition: | Aluminum | 10.84 % | Al | 20.48 % | Al2O3 |
| Iron | 33.66 % | Fe | 43.30 % | FeO | |
| Silicon | 16.93 % | Si | 36.21 % | SiO2 | |
| Oxygen | 38.57 % | O | |||
| 100.00 % | 100.00 % | = TOTAL OXIDE |
| Crystallography: | Isometric – Hexoctahedral |
| Crystal Habit: | Typically well-formed dodecahedra or trapezohedra, to 1 m; also in rounded grains and massive. |
| Twinning: | None |
| Cleavage: | Parting on {110} |
| Fracture: | Subconchoidal |
| Tenacity: | Brittle |
| Moh’s Hardness: | 7.0 – 7.5 |
| Density: | 4.318 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioactive |
| Color: | Deep red, brownish red, red-violet, black; may be sectored. |
| Transparency: | Transparent to Translucent |
| Luster: | Vitreous to Resinous |
| Refractive Index: | 1.830 Isotropic |
| Birefringence: | 0.000 (Isotropic) |
| Dispersion: | Weak |
| Ultraviolet Fluorescence: | inert |
| Pleochroism: |
None |
