metamorphic

Garnet-bearing metamorphic rock, likely mica schist

Biotite–garnet schist; commonly includes quartz, feldspar, biotite, and almandine garnet

AI-generated identification · may be incorrect

Typically medium- to coarse-grained, dark brown/black and sparkly, with reddish garnet crystals and flaky mica; Mohs hardness is about 2.5–7 depending on mineral, with mica schistosity and garnet’s lack of cleavage. The attached pale gray-white crystals may be quartz or feldspar.

Identified August 12, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when shale or another clay-rich sediment was subjected to regional heat and pressure during mountain building, commonly during the Paleozoic or Precambrian. Garnet grew during metamorphic recrystallization.

Uses & applications

Used mainly as a decorative stone, lapidary material, and teaching or collecting specimen; rarely used structurally because schist splits along foliation.

Geological facts

Garnet-bearing schists record metamorphic pressure-temperature conditions and can indicate medium- to high-grade metamorphism. Garnet composition is often almandine-rich, with formula Fe₃Al₂(SiO₄)₃.

Field identification & locations

Identify it by visible foliation, glittering mica flakes, and embedded reddish garnets; quartz is glassy and feldspar is commonly blocky and pale. Common in metamorphic belts worldwide, including the Appalachians, New England, Scandinavia, and the Alps.