metamorphic
Glaucophane Schist (Blueschist)
Glaucophane Schist
Hardness: 5-6 (Mohs), Color: Blue to grayish-blue or green, Luster: Silky or pearly to earthy, Structure: Foliated or schistose, Specific Gravity: 3.0-3.15
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Physical properties
Hardness: 5-6 (Mohs), Color: Blue to grayish-blue or green, Luster: Silky or pearly to earthy, Structure: Foliated or schistose, Specific Gravity: 3.0-3.15
Formation & geological history
Formed under conditions of high pressure and relatively low temperature (subduction zones). These rocks typically date from the Phanerozoic eon and represent metamorphosed oceanic crust.
Uses & applications
Primarily used for geological research and as an indicator of ancient plate tectonic boundaries; also collected by hobbyists.
Geological facts
Blueschist is a signature rock of subduction zones, proving that a specific area was once located deep within a convergent plate boundary. It often contains minerals like lawsonite, jadeite, or epidote.
Field identification & locations
Look for the distinctive blue-gray hue and fine-grained foliated texture. Common in the Franciscan Complex of California, Italy, and Japan.
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