Tuesday, February 14, 2012

My Igneous Rock! Lab #4

Diorite

  • intermediate composition between felsic and mafic
  • classically a salt and pepper rock
  • white to light gray plagioclase and black hornblende
  • some diorites contain biotite as well as hornblende, and some contain up to 10% quartz
  • If you have more than 10% quartz, you probably have a granite on your hands. If you clearly have abundant K-feldspar, you probably have a granite on your hands. 
  • Diorite occurs in small bodies such as sills, dikes, stocks, or as more irregular masses associated with gabbro and batholiths of granodiorite and granite.

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