Volcanoes have done wonderful things for the Earth. They helped cool off
the earth removing heat from its interior. Volcanic emissions have produced
the atmosphere and the water of the oceans. Volcanoes make islands and add
to the continents. Volcanic deposits are also used as building materials.
In the 1960’s Robert Bates published Geology of the Industrial Rocks and
Minerals. He noted that basalt and diabase are quarried in the northeastern
and northwest states. Most of the basalt and diabase is used for crushed stone:
concrete aggregate, road metal, railroad ballast, roofing granules, and riprap.
High-denisity basalt and diabase aggregate is used in the concrete shields of
nuclear reactors. Some diabase is used for dimension stone (“black granite”).
Pumice, volcanic ash, and perlite are mined in the west. Pumice and volcanic ash
are used as abrasives, mostly in hand soaps and household cleaners. The finest
grades are used to finish silverware, polish metal parts before electroplating,
and for woodworking. Bates reports that in ancient Rome lime and volcanic ash
were mixed to make cement. In modern times pumice and volcanic ash have been used
to make cement for major construction projects (dams) in California and Oklahoma.
Pumice and volcanic ash continue to be used as lightweight aggregate in concrete,
especially precast concrete blocks. Crushed and ground pumice are also used for
loose-fill insulation, filter aids, poultry litter, soil conditioner, sweeping
compound, insecticide carrier, and blacktop highway dressing. Perlite is volcanic
glass (made of rhyolite) that has incorporated 2-5% water. Perlite expands rapidly
when heated. Perlite is used mostly as aggregate in plaster. Some perlite is used as
aggregate in concrete, especially in precast walls.