metamorphic
Micaceous schist (likely garnet-mica schist)
Muscovite–biotite schist, possibly garnet-bearing; chiefly quartz, mica, and feldspar
AI-generated identification · may be incorrectTypically Mohs 2–7 depending on minerals; brown, silvery, and gray with a sparkly micaceous luster and strongly foliated, flaky texture. The visible sheen suggests aligned muscovite/biotite; crystal grains are too coarse and weathered for definitive identification from the image.
Identified More metamorphic →
Explore Micaceous schist (likely garnet-mica schist) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Typically Mohs 2–7 depending on minerals; brown, silvery, and gray with a sparkly micaceous luster and strongly foliated, flaky texture. The visible sheen suggests aligned muscovite/biotite; crystal grains are too coarse and weathered for definitive identification from the image.
Formation & geological history
Formed when shale or other aluminous sedimentary rock underwent regional metamorphism under elevated pressure and temperature, commonly during mountain building. Its exact geological age cannot be determined visually; schists occur from Precambrian to younger orogenic belts.
Uses & applications
Used locally as decorative stone, landscaping material, and occasionally wall or veneer stone, though foliation limits structural use. Attractive mica-rich pieces have modest collector value.
Geological facts
The glitter comes from light reflecting off cleavage surfaces of mica, not necessarily from metallic minerals. Schistosity records directed metamorphic pressure and commonly causes the rock to split into thin plates.
Field identification & locations
Identify it by pronounced foliation, glittery mica flakes, uneven gray-brown color, and a tendency to break along planar surfaces; a streak, hardness, and acid test can refine identification. Common in metamorphic mountain belts worldwide, including the Appalachians, Alps, Himalayas, and New England.
More like this
