The igneous rocks are commonly acid intrusives of a granite or porphyry type, less commonly intrusives of gabbro and diabase and surface lavas of rhyolite and basalt.
"The Economic Aspect of Geology"
C. K. Leith
The domestic production has been small, consisting principally of flint pebbles from the California beaches, and artificial pebbles made from rhyolite in Nevada and quartzite in Iowa.
"The Economic Aspect of Geology"
C. K. Leith
"Better in the little cemetery at rhyolite," answered the other.
"The Boy With the U. S. Survey"
Francis Rolt-Wheeler