Halite
Sodium
Chloride
NaCl
Halite,
better known as rock salt, can easily be distinguished by its taste.
Since taste is an important property of salt, there is a right way to
taste a specimen of halite (or an unknown mineral that is similar to
halite) and a wrong way. The right way is to first lick your index
finger, rub it against the specimen and then taste the finger. This
limits the amount of the mineral that actually gets in your mouth, an
important consideration when you consider that there are poisonous
minerals that resemble halite.
Halite is found in many current evaporative deposits such as near
Salt Lake City, Utah and Searles Lake California in the U.S., where it
crystallizes out of evaporating brine lakes. It is also found in
ancient bedrock all over the world where large extinct salt lakes and
seas have evaporated millions of years ago, leaving thick deposits of
salt behind. The cities of Cleveland and Detroit rest above huge
halite deposits that are mined for road salt.
Perfectly formed cubes of halite are typical of the habit of this
mineral. However it does form some unusual interesting habits that are
much sought after by collectors. One habit is called a hopper crystal
which forms what has been termed a skeleton of a crystal. Just the
edges of a hopper crystal extend outward from the center of the
crystal leaving hollow stairstep faces between these edges. Hopper
crystals form due to the disparity of growth rates between the crystal
edges and the crystal faces.
Another habit of interest is the vein filling fibrous habit found at
Mulhouse, France and at some other locallities. Often specimens are
brightly colored purple and blue and with the silky luster due to the
fibers, they represent a wonderful and a very uncharacteristic variety
of halide. These specimens are a must have for teachers of mineral
identification classes that want a stumper for those end of the
session ID exams. Of course they are still easy to identify with the
oft forgot simple taste test.
Well crystallized specimens of halite cubes can be very impressive
and popular. Some are colored an attractive pastel pink by inclusions
of bacterial debris that are trapped during crystallization in an
evaporative lake. Often these specimens that are sold world wide in
rock shops and in mineral shows where grown within the past year. In
fact, the crystals form so fast and so well in some evaporative lakes
that mineral dealers are using their imaginations to enhance their
inventory. They are putting sticks, animal skulls and other
imaginative items into these lakes and retrieving them a relatively
short time later covered in clusters of white or pink halite cubes.
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