Gypsum
An important construction material that has been used for
thousands of years
Article by: Hobart
M. King, PhD, RPG
What
is Gypsum?
Gypsum
is an evaporite mineral most commonly found in layered sedimentary deposits in
association with halite, anhydrite, sulfur, calcite, and dolomite.
Gypsum
(CaSO4.2H2O) is very similar to Anhydrite (CaSO4).
The
chemical difference is that gypsum contains two waters and anhydrite is without
water.
Gypsum
is the most common sulfate mineral.
Uses
of Gypsum
Gypsum
uses include: manufacture of wallboard, cement, plaster of Paris, soil
conditioning, a hardening retarder in portland cement.
Varieties
of gypsum known as "satin spar" and "alabaster" are used
for a variety of ornamental purposes; however, their low hardness limits their
durability.
|
Physical
Properties of Gypsum |
|
|
Chemical Classification |
Sulfate |
|
Color |
Clear, colorless, white, gray, yellow, red, brown |
|
Streak |
White |
|
Luster |
Vitreous, silky, sugary |
|
Diaphaneity |
Transparent to translucent |
|
Cleavage |
Perfect |
|
Mohs Hardness |
2 |
|
Specific Gravity |
2.3 |
|
Diagnostic Properties |
Cleavage, specific gravity, low hardness |
|
Chemical Composition |
Hydrous calcium sulfate, CaSO4.2H2O |
|
Crystal System |
Monoclinic |
|
Uses |
Used to manufacture dry wall, plaster, joint compound.
An agricultural soil treatment. |
Hobart M. King, Ph.D., GIA GG
Hobart M. King is the manager
and publisher of Geology.com. He is a geologist with over 40 years of
experience, has a Ph.D. in geology, and is a GIA graduate gemologist. Much of
his work has focused on coal geology, industrial minerals, gemology, geologic hazards,
and geoscience education.
He has authored many of the
internet’s most popular articles about rocks, minerals and gems. He writes most of the content
published on Geology.com and compiles its daily news. His writing is read by
over a million people each month, making him one of the world’s most widely
read geologists.
Dr. King earned a Ph.D. and an
M.S. in geology from West Virginia University; a B.S. in geology from
California University of Pennsylvania; and, a Graduate Gemologist Diploma from
the Gemological Institute of America. He is a registered professional geologist
in the Commonwealth of Pennsylvania.
He has worked as a geologist
in a variety of settings since 1975.
https://geology.com/minerals/gypsum.shtml
Gypsum: Satin spar, a fibrous variety of gypsum from
Derbyshire, England. Specimen is approximately 4 inches (10 centimeters) across.
Gypsum wallboard and plaster: Wallboard and
construction plaster are the primary industrial uses of gypsum in the United
States.
Alabaster Gypsum: Alabaster, a
variety of gypsum, from Pomaia, Italy. Specimen is approximately 3 inches (7.6
centimeters) across.
Gypsum from Michigan: Gypsum from
Grand Rapids, Michigan. Specimen is approximately 4 inches (10 centimeters)
across.
Gypsum translucency: The
translucent characteristic of alabaster, a variety of gypsum, from Pomaia,
Italy. Specimen is approximately 3 inches (7.6 centimeters) across.
Alabaster gypsum jar: Jar made of
beautiful translucent alabaster gypsum by David MacFarlane
Selenite Gypsum: Selenite, a
variety of gypsum from Penfield, New York. Specimen is approximately 2-1/2
inches (6.4 centimeters) across.
Gypsum from New York: Selenite, a
variety of gypsum from Penfield, New York. Specimen is approximately 2-1/2
inches (6.4 centimeters) across.
Gypsum from Virginia: Gypsum from
North Holston, Virginia. Specimen is approximately 1-1/2 inches (3.8
centimeters) across.
Satin spar Gypsum: Satin spar, a
fibrous variety of gypsum from Derbyshire, England. Specimen is approximately 3
inches (7.6 centimeters) across.
No comments:
Post a Comment