Schist
Image: James St. John (CC BY 2.0)
Mineral NameSchist
Chemical FormulaVariable (composed of various minerals)
Mohs HardnessVariable (typically 3-7, depending on mineral composition)
Streak ColorVariable; often white or light gray
CleavageExhibits schistosity (foliation), splitting easily along planes of platy or elongated minerals.
FractureUneven, splintery, or platy along foliation
Specific GravityVariable (typically 2.6-3.0, depending on mineral composition)
Colorslight gray, silver, dark gray, black
TransparencyOpaque
Type Localityroadcut on the northern side of Route 9, west of the town of Marlboro, southern Vermont, USA
Mineral GroupMetamorphic rock
Usesconstruction material, decorative stone, landscaping
Associated Mineralshornblende, chlorite, quartz, amphibole
Raritycommon
Description
This metamorphic rock displays a light gray to silver matrix with abundant dark gray to black radiating, needle-like crystals of hornblende amphibole, creating a striking, textured surface.
Geological Context
This Ordovician-aged schist formed within a highly sheared serpentinite belt, indicating significant regional metamorphism and deformation. It is found alongside chlorite schist, amphibolite, and quartz veins.
