Name:   Hornblende Gabbro 

Geologic Name:  Salem gabbro (-diorite)

Reference: Clapp, C.H., Geology of the igneous rocks of Essex County,
Massachusetts: U.S. Geol. Survey Bull. 704, pp. 21-23, 36-42, 1921.

Microscopic characters:  Hypautomorphic-granular textrue.  The essential
minerals are labradorite showing sharp albite twinning, biotite, brown
hornblende and diallage.  Also a few skeletal growths of olivine and magnetite.
Apatite crystals, magnetite and pyrrhotite are abundant accessories, with
occassional grains of orthoclase and quartz.  Some chlorite is associated 
with the femic mineral.