Granite is an
that is composed of four minerals.
These minerals are quartz, feldspar, mica, and usually
Granite forms as magma cools far under the earth's surface.
Because it hardens deep underground it cools very slowly. This allows crystals
of the four minerals to grow large enough to be easily seen by the naked eye.
Granite - 2:
intrusive igneous rock
with at least 65% silica.
Quartz, plagioclase feldspar and potassium feldspar make up most
of the rock and give it a fairly light color. Granite has more potassium
feldspar than plagioclase feldspar. Usually with biotite, but also may
Granite - 3:
Intrusive igneous rocks,
granite is a felsic rock with dominant minerals --
orthoclase (a pink, potassium-rich variety
of feldspar), quartz, and lesser amounts of mica (both silvery
muscovite or black biotite),
(white to gray,sodium-rich varieties of feldspar). Note that
the word "granite" is used fairly liberally. Many rocks called
"granite" are technically something different. The word
"granitoid" or "granitic" implies felsic to intermediate
intrusive rocks of many varieties, including granite.
A general term for
intrusive igneous rocks
that look similar to granite but may range in composition from quartz-diorite to granite. All granitic rocks are light colored; feldspar and quartz are visible in hand specimen.
Granite as a Building Material:
Granite is an excellent material for building bridges and buildings
because it can withstand thousands of pounds of pressure. It is also
used for monuments because it weathers slowly.
Engravings in the granite can be read for hundreds of years, making the rock more
Granite is quarried in many places in the world including the United States.
The "Granite State":
The State of New Hampshire has the nickname "Granite
State" because of the amount of granite in the mountains of that beautiful state.
The Canadian Shield:
The Canadian Shield of North America contains huge
outcroppings (surface rocks) of granite.
-- Excerpts from:
Volcano World Website, July 2001,
USGS/NPS Geology in the Parks Website, 2003