metamorphic
Garnet in Matrix
Almandine or Pyrope Garnet (X3Y2(SiO4)3) in Schist or Eclogite matrix
Hardness: 6.5-7.5 (garnets); Color: deep red to reddish-brown crystals in a light tan or greyish matrix; Luster: vitreous to resinous; Crystal structure: isometric/dodecahedral
- Hardness
- 6
- Luster
- vitreous to resinous
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Physical properties
Hardness: 6.5-7.5 (garnets); Color: deep red to reddish-brown crystals in a light tan or greyish matrix; Luster: vitreous to resinous; Crystal structure: isometric/dodecahedral
Formation & geological history
Forms under high pressure and temperature during regional metamorphism of clay-rich sedimentary rocks (shale) or mafic igneous rocks. Most commonly found in mica schists or gneisses.
Uses & applications
Used as an abrasive (sandpaper, waterjet cutting), gemstones in jewelry, and as an index mineral for geologists to determine metamorphic history.
Geological facts
Garnets are one of the most diverse mineral groups and can be found in almost every color except blue. They have been used as gemstones since the Bronze Age.
Field identification & locations
Identify by the characteristic round 'porphyroblast' shapes (often 12-sided) embedded in a softer matrix. Common in metamorphic belts like the Appalachians, Alps, and Himalayas.
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