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Quartz Diorite
Source:
Billings M.P.
Credit Line: Mineralogical and Geological Museum at Harvard University
Object number: BILLINGS-W-173
DescriptionIgneous rock which contains mainly quartz (≤ 4 mm), black mica (biotite, ≤ 3.5 mm), and minor amounts of feldspar. The side where the label was painted on may be a scrape where magma dragged along another rock surface.