Garnet Mica Schist
“Glittering garnets in a mica matrix”
Garnet mica schist is a medium- to high-grade metamorphic rock studded with visible garnet crystals set in a shimmering matrix of mica. The growth of garnet indicates temperatures and pressures higher than ordinary mica schist, making these rocks valuable indicators of metamorphic conditions.
garnet (almandine), muscovite, biotite, quartz, feldspar, staurolite (occasional)
Manhattan (New York, USA), Scottish Highlands, Barrovian zones (Scotland), Alps, New England (USA)
5-7
Manhattan Island's bedrock includes garnet mica schist — the garnets embedded in it are the official state gemstone of New York and can still be found in Central Park outcrops.
Test Your Knowledge
What do the size and chemical zoning of garnets in mica schist reveal to petrologists?
Photo Attribution
Author: James St. John
License: CC BY 2.0
Related Specimens
Want to identify rocks yourself?