DIABASE and TRAPROCK
Diabase:
A dark-gray to black, fine-textured
igneous rock
composed mainly of feldspar
and pyroxene and used for monuments and as crushed stone.
Trap Rock:
Any of various dark-colored fine-grained
igneous rock
(as
basalt)
used especially in road making
-- Excerpts from:
The American Heritage Dictionary of the English Language, Fourth Edition, 2000, Online Version
|