metamorphic
Sapphirine in Magnesian Schist
Sapphirine: (Mg,Al)8(Al,Si)6O20
Hardness: 7.5 Mohs scale. Color: Dark blue to grey-green. Luster: Vitreous. Crystal Structure: Monoclinic or Triclinic. Cleavage: Poor. Specific Gravity: 3.4–3.5.
- Hardness
- 7
- Color
- Dark blue to grey-green
- Luster
- Vitreous
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Physical properties
Hardness: 7.5 Mohs scale. Color: Dark blue to grey-green. Luster: Vitreous. Crystal Structure: Monoclinic or Triclinic. Cleavage: Poor. Specific Gravity: 3.4–3.5.
Formation & geological history
Formed under high-grade metamorphic conditions (granulite facies) involving high temperature and pressure in silica-poor, magnesium-aluminum rich environments. Often found in Precambrian metamorphic belts.
Uses & applications
Primarily used as a rare collector's mineral. High-quality transparent crystals are occasionally faceted into gemstones for jewelry, though rarity limits commercial use.
Geological facts
Despite its name, it is not a sapphire (corundum); it was named for its sapphire-like blue color. It is often associated with other rare minerals like kornerupine and phlogopite mica.
Field identification & locations
Identify by its dark blue grains within a lighter matrix (usually feldspar or quartz) and its extreme hardness. Found in locations like Greenland, Madagascar, and the Italian Alps. Collectors should look for distinct blue patches in granulite-rich terrains.
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