Name:   Diabase Porphyry

Geologic Name:  None

Reference:  Dale, T.N., The commercial granites of New England: U.S. Geol.
Survey Bull. 738, p. 303, 1923.

Microscopic characters:  Porphyritic texture with large phenocrysts of 
andesine-labradorite.  The groundmass is a rather confused aggregate
of plagioclase (andesine-labradorite), augite partially altered to uralite, 
and biotite partly altered to chlorite.  Titanite, a small amount of pyrite,
abundant magnetite, crystals of apatite and a few crystals of zircon 
constitute the accessory minerals.  There is a small amount of secondary
calcite.
