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GeoSnaps - Image of the Day

Geologic snapshots capturing Arizona’s geologic setting and mining history with a picture of the day from 1 January through 31 December 2013.

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Thursday, December 19, 2013
layered pegmatite, granite intrusion

Santa Catalina Mountains | Pima County, Arizona

Thin layers with high concentrations of fine garnet crystals in Eocene pegmatitic granite near Marshall Gulch in the Santa Catalina Mountains. These are known as garnet “schlieren”. Head of rock hammer for scale. (Photo by Jon Spencer)