File:Garnet-biotite rock, Beartooth Mountains MT.jpg
Garnet-biotite rock (3.8 cm across at its widest) from the Precambrian of Montana, USA.
This gorgeous rock is dominated by deep red, rounded garnet crystals and lustrous black biotite mica. It is from an alteration halo around Archean-aged, magnetite-rich meta-iron formation. It, and the enclosed meta-iron formation, formed during two metamorphic episodes in the Precambrian: one in the Paleoarchean, at about 3.4 Ga (granulite-facies metamorphism) and another at about 2.8 Ga (upper amphibolite facies metamorphism).
Locality: Quad Creek section (= locality of Mueller et al., 1987, Geological Society of America Centennial Field Guide, Rocky Mountain Section, pp. 75-76) - roadcut on southern side of Beartooth Highway (Rt. 212), immediately west of Quad Creek, between milepost 50 and milepost 51, southern side of Rock Creek Canyon, just north of the eroded edge of Beartooth Plateau, southwest of the town of Red Lodge, Beartooth Mountains, southern Montana, USA (45° 01' 41.27" North & 109° 24' 55.31" West).
|Source||Garnet-biotite rock (alteration halo around magnetite-rich meta-iron formation) (Archean, metamorphism at about 3.4 Ga & about 2.8 Ga; Quad Creek section - roadcut along the Beartooth Highway, Beartooth Mountains, southern Montana, USA)|
|Author||James St. John|
|This file is licensed under the Creative Commons Attribution 2.0 Generic license.|
|This image was originally posted to Flickr by jsj1771 at https://www.flickr.com/photos/47445767@N05/15216910771. It was reviewed on by FlickreviewR and was confirmed to be licensed under the terms of the cc-by-2.0.|
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|current||23:53, 13 September 2014||2,188 × 2,192 (2.71 MB)||Tillman||Transferred from Flickr via Flickr2commons|
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