English: Chrysotile from the Ordovician of Quebec, Canada.

Chrysotile is a serpentine-group mineral having the formula Mg3Si2O5(OH)4 - magnesium hydroxy-silicate. It has a greenish to whitish color, a nonmetallic, silky luster, a white streak, is moderately soft (about 2.5 on the Mohs Hardness Scale), and has a fibrous fracture - the fibers are flexible. Chrysotile is often referred to as "white asbestos".

Chrysotile is a component of many serpentinites, a light green to dark green to blackish colored metamorphic rock. Serpentinites form by metamorphism of olivine-rich peridotites in the presence of water. If chrysotile is present, it's often in the form of "veins" - fractures subsequently filled with white asbestos fibers. The Thetford, Quebec sample seen here is a from a chrysotile vein. This type of occurrence has been called "vein serpentinite" (e.g., Coleman, 1971). Thetford area serpentinites represent ancient oceanic lithosphere peridotites that were metamorphosed during the Taconic Orogeny in the Ordovician.

Geologic unit: Thetford Mines Ophiolite Complex, Ordovician

Locality: undisclosed/unrecorded site at or near the town of Thetford (Thetford Mines) (but likely from an asbestos mine), southeastern Mégantic County, southern Quebec, Chaudiere Appalachians, south of the St. Lawrence River, southeastern Canada

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Reference cited:

Coleman (1971) - Petrologic and geophysical nature of serpentinites. Geological Society of America Bulletin 82: 897-918.