metamorphic
Garnet-bearing Schist / Conglomerate Specimen
Metamorphic rock with almandine garnet porphyroblasts
Hardness varies from 6.5 to 7.5 for the garnet crystals and around 3-4 for the host matrix; color is brownish-gray with reddish-brown embedded crystals; luster is vitreous to resinous in the crystals; crystal structure is isometric for garnet; specific gravity ranges from 3.5 to 4.3.
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Physical properties
Hardness varies from 6.5 to 7.5 for the garnet crystals and around 3-4 for the host matrix; color is brownish-gray with reddish-brown embedded crystals; luster is vitreous to resinous in the crystals; crystal structure is isometric for garnet; specific gravity ranges from 3.5 to 4.3.
Formation & geological history
Formed through regional metamorphism of clay-rich sedimentary rocks under high temperature and pressure, typically occurring during continental collision events over millions of years.
Uses & applications
Used primarily as educational specimens, mineral collecting, lapidary cabochons, and occasionally abrasive industrial applications.
Geological facts
Garnets form as porphyroblasts, growing larger than the surrounding fine-grained matrix minerals as the rock undergoes intense pressure and temperature changes.
Field identification & locations
Identify by looking for distinct, reddish-brown, dodecahedral or rounded crystal grains embedded within a smoother, weathered rock matrix. Found globally in metamorphic terranes such as New England, USA, and various Scandinavian regions.
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