| Spessartine | |
| Category: | Nesosilicate Garnet group |
| Formula: | Mn2+3Al2(SiO4)3 |
| Imasymbol: | Sps[1] |
| Strunz: | 9.AD.25 |
| System: | Isometric |
| Class: | Hexoctahedral (mm) H-M symbol: (4/m 2/m) |
| Symmetry: | Ia3d |
| Unit Cell: | a = 11.63 Å; Z = 8 |
| Color: | Yellow through red |
| Habit: | Massive to crystalline |
| Cleavage: | None |
| Fracture: | Sub-conchoidal |
| Tenacity: | Brittle |
| Mohs: | 6.5 – 7.5 |
| Luster: | Vitreous |
| Refractive: | 1.800 |
| Opticalprop: | Isotropic, often anomalous double refractive |
| Birefringence: | none |
| Dispersion: | Weak |
| Absorption: | Bands at 410, 420, 430 nm (or merging to form cutoff below 430 nm; also bands at 460, 480, 520 nm. Possible weak bands at 504 or 573 nm |
| Streak: | White |
| Gravity: | 4.19 calculated, 4.12 – 4.32 measured |
| Diaphaneity: | Transparent to translucent |
| References: | [2] [3] [4] |
Spessartine is a nesosilicate, manganese aluminium garnet species, Mn2+3Al2(SiO4)3.[5] [2] [3] [4] This mineral is sometimes mistakenly referred to as spessartite.[6]
Spessartine's name is a derivative of Spessart in Bavaria, Germany, the type locality of the mineral.[2] [3] It occurs most often in granite pegmatite[2] [3] [4] and allied rock types and in certain low-grade metamorphic phyllites. Sources include Australia, Myanmar, India, Afghanistan, Israel, Madagascar, Namibia, Nigeria, Mozambique, Tanzania and the United States.[5] Spessartine of an orange-yellow has been called Mandarin garnet and is found in Madagascar. Violet-red spessartines are found in rhyolites in Colorado and Maine. In Madagascar, spessartines are exploited either in their bedrock or in alluvium. The orange garnets result from sodium-rich pegmatites. Spessartines are found in bedrock in the highlands in the Sahatany valley. Those in alluvium are generally found in southern Madagascar or in the Maevatanana region.[7] [8] [9] [10] [11]
Spessartine forms a solid solution series with the garnet species almandine.[3] [4] Well-formed crystals from this series, varying in color from very dark-red to bright yellow-orange, were found in Latinka, Rhodope Mountains, Kardzhali Province, Bulgaria.[12] Spessartine, like the other garnets, always occurs as a blend with other species. Gems with high spessartine content tend toward a light orange hue, while almandine prevalence induces red or brownish hues.[13]