Limestone
Limestone is a sedimentary
rock, composed mainly of skeletal
fragments of marine organisms such
as coral, forams, and mollusks. Its
major minerals are the minerals
calcite and aragonite, which are
different crystal forms of calcium
carbonate (CaCo3).
COLOR: It is ordinarily white, but may be colored by impurities, iron oxide making it
brown, yellow, or red and carbon making it blue, black, or gray.
STREAK: White LUSTER: Dull to Pearly
HARDNESS: 3-4 DENSITY: 2.3-2.7g/cm3
CLEAVAGE: Non-existent FRACTURE: Splintery
GRAIN SIZE: Fine Grained TRANSPERANCY: Opaque
Limestone can be considered as the following:
Chemical sedimentary rock – formed by the
precipitation of calcium carbonate from lake or
ocean water.
Ex. Tufa
Biological sedimentary rock – contains remains of
marine organisms/skeletal fragments of marine organisms
(corals, mollusks and etc.)
Ex. Chalk
Limestone is composed primarily of 50% Calcium carbonate (CaCO3) in the
form of calcite. All limestones contain at least a few percentages of other materials,
such as quartz, feldspar, clay materials, pyrite, siderite
and etc.
Limestones are mostly found in shallow, calm,
and warm marine waters. Others are found in caves,
which are formed through evaporation, like Stalactites
and Stalagmites.
Stalactites (which is also a chemical sedimentary rock)
are formed when droplets of water seep down from above the
cave and evaporate before falling to the cave floor. When the
water evaporates, the calcium carbonate that was dissolved in
the water will be deposited on the cave ceiling. If the droplet falls
to the floor and evaporates there, a stalagmite could grow
upwards from the cave floor.
Varieties of Limestone
Chalk – remains of marine organisms
Tufa – produced by precipitation of calcium-laden waters at a hot
spring, lake shores, or other locations.
Uses of Limestone
For construction
The Great Pyramid of Giza has an outside cover made entirely from
limestone.
“The Giza Pyramids, built to
endure an eternity, have done just
that. The monumental tombs are
relics of Egypt's Old Kingdom era and
were constructed some 4,500 years
ago.”
-National Geographic
Used in making cement.
