Spessartite is an orange to orange-red form of the gemstone Garnet. The term Garnet describes a group name for several closely related minerals that form important gemstones, and Spessartite is an individual member mineral of the Garnet group.
Spessartite garnet is ideochromatic, meaning that it is colored by a fundamental element in its composition. That element is manganese, which produces an orange color. Take away the manganese, and it would no longer be spessartite. Thus spessartite has only one basic color – orange.
Spessartine is formed in manganese rich metamorphic environments and in some granitic pegmatites.
|Naturally Etched Garnet Almandine-Spessartine. From Navegadora claim, Minas Gerais, Brazil |
Photo by Enrico Bonacina
Properties of Spessartine
- Formula: Mn2+3Al2(SiO4)3
- Color is orange, reddish brown, brown, pink and yellow.
- Luster is vitreous.
- Transparency crystals are transparent to translucent.
- Crystal System is isometric; 4/m bar 3 2/m
- Crystal Habits include the typical rhombic dodecahedron. But more commonly is found as the 24 sided trapezohedron. Combinations of these forms are common and sometimes the rare faces of the hexoctahedron, a 48 sided crystal habit that rarely is seen by itself, can also combine with these other forms making very attractive, complex and multifaceted crystals. Massive and granular occurrences are also seen.
- Cleavage is absent.
- Fracture is conchoidal.
- Hardness is 7
- Specific Gravity is approximately 4.19 or less (above average for translucent minerals).
- Streak is white.
- Associated Minerals are feldspars, quartz, tourmalines, topaz, beryl, rhodonite and other manganese minerals.
- Other Characteristics: index of refraction is 1.80
- Notable Occurrences are Pakistan; Madagascar; Brazil and Sri Lanka.
- Best Field Indicators are crystal habit, color, and hardness.