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Marble
Marbles often
occur inter-bedded with such metamorphic rocks as mica schists,
phyllites, gneisses, and granulites and are most common in the
older layers of the earth's crust that have been deeply buried
in regions of extreme folding and igneous intrusion. The change
from linestones rich in fossils into true marbles in such metamorphic
regions is a common phenomenon.
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Granite
Granite is
a tough, durable rock composed primarily of three different minerals.
These minerals are easy to see due to their different colors. The
white mineral grains found in granite are feldspar. It is the most
abundant mineral found in granite. The light gray, glass-like grains
are quartz, and the black, flake-like graines are biotite or black
mica.
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Travertine
Travertine is
a dense, closely compacted form of limestone found mostly in banded
layers. Most travertine is white or cream colored. The stone consists
mainly of calcium carbonate. Travertine deposits occur specifically
in areas with circulating ground water containing calcium carbonate.
Travertine often forms around the mouths of hot springs. The word
travertine comes from the ancient roman name for Tivoli, a town
in Italy near large deposits of travertine.
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Limestone
Limestone has
five categories: French Coral, Texas Limestone, Hauteville, Indiana
Limestone and Jeruselem Limestone. Limestone dissolves in rainwater
more easily than other rocks. Rainwater picks up a small amount
of carbon dioxide during its passage through the air, and that
turns it into a very weak acid. Calcite is vulnerable to acid.
That explains why underground caverns tend to form in limestone
country, and why limestone buildings suffer from acid rainfall.
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