Name:   Diabase

Geologic Name:  Medford Diabase

Reference:  Hobbs, W.H., On the petrographical character of a dike of diabase
in the Boston Basin: Bull. of the Museum of Comparative Zoology, Harvard,
vol. XVI, #1, 1888.

Microscopic characters:  Coarse diabase texture.  The principal constituent
is labradorite filled with flakes and shreds of sericite.  Biotite is partially altered 
to chlorite and chlorite also fills interstices between the fledspar laths.  Brown
hornblende is less common.  Titaniferous magnetite partially altered to 
leucoxene, titanite both primary and secondary, large apatite crystals and
small grains of pyrite are the accessory constituents.  Secondary calcite
is quite abundant.
