Name:  Quartz Keratophyre (Quartz Felsite Porpphyry)

Geologic Name:  Lynn quartz keratophyre

Reference:  Clapp, C.H., Geology of the igneous rocks of Essex County, Massachusetts:
U.S. Geol. Survey Bull. 704, p. 30-31, 69-71, 1921.

Microscopic characters:  Porphyritic texture.  The phenocrysts are principally plagioclase
with irregular inclusions of epidote.  There are a few quartz crystals and biotite flakes
altered to chlorite.  Apatite and magnetite occur as accessory minerals.  The ground-
mass is composed of a fine crystalline aggregate of quartz, feldspar, chlorite, magnetite
and leucoxene.