Description:
Fluorite is a mineral with a veritable bouquet of brilliant
colors. Fluorite is well known and prized for its glassy
luster and rich variety of colors. The range of common
colors for fluorite starting from the hallmark color
purple, then blue, green, yellow, colorless, brown,
pink, black and reddish orange is amazing and is only
rivaled in color range by quartz. Intermediate pastels
between the previously mentioned colors are also possible.
It is easy to see why fluorite earns the reputation
as "The Most Colorful Mineral in the World".
The many colors of fluorite are truly wonderful. The
rich purple color is by far fluorite's most famous and
popular color. It easily competes with the beautiful
purple of amethyst. Often specimens of fluorite and
amethyst with similar shades of purple are used in mineral
identification classes to illustrate the folly of using
color as the sole means to identify minerals. The blue,
green and yellow varieties of fluorite are also deeply
colored, popular and attractive. The colorless variety
is not as well received as the colored varieties, but
their rarity still makes them sought after by collectors.
A brown variety found in Ohio and elsewhere has a distinctive
iridescence that improves an otherwise poor color for
fluorite. The rarer colors of pink, reddish orange (rose)
and even black are usually very attractive and in demand.
Most specimens of fluorite have a single color, but
a significant percentage of fluorites have multiple
colors and the colors are arranged in bands or zones
that correspond to the shapes of fluorite's crystals.
In other words, the typical habit of fluorite is a cube
and the color zones are often in cubic arrangement.
The effect is similar to phantomed crystals that appear
to have crystals within crystals that are of differing
colors. A fluorite crystal could have a clear outer
zone allowing a cube of purple fluorite to be seen inside.
Sometimes the less common habits such as a colored octahedron
are seen inside of a colorless cube. One crystal of
fluorite could potentially have four or five different
color zones or bands. To top it all off, fluorite is
frequently fluorescent and, like its normal light colors,
its fluorescent colors are extremely variable. Typically
it fluoresces blue but other fluorescent colors include
yellow, green, red, white and purple. Some specimens
have the added effect of simultaniously having a different
color under longwave UV light from its color under shortwave
UV light. And some will even demonstrate phosphorescence
in a third color! That's four possible color luminescence
in one specimen! If you count the normal light color
too. The blue fluorescence has been attributed to the
presence of europium ions (Eu +2). Yttrium is the activator
for the yellow fluorescence. Green and red fluorescent
activation is not exactly pinned down as of yet, but
may be due to the elements already mentioned as well
as other rare earth metals; also manganese, uranium
or a combination of these. Even unbonded fluorine trapped
in the structure has been suggested. The word fluorescent
was derived from fluorite since specimens of fluorite
were some of the first fluorescent specimens ever studied.
The naming followed the naming precedence set by opalescence
from opal; ergo fluorescence from fluorite. Another
unique luminescent property of fluorite is its thermoluminescence.
Thermoluminescence is the ability to glow when heated.
Not all fluorites do this, in fact it is quite a rare
phenomenon. A variety of fluorite known as "chlorophane"
can demonstrate this property very well and will even
thermoluminesce while the specimen is held in a person's
hand activated by the person's own body heat (of course
in a dark room, as it is not bright enough to be seen
in daylight). The thermoluminescence is green to blue-green
and can be produced on the coils of a heater or electric
stove top. Once seen, the glow will fade away and can
no longer by seen in the same specimen again. It is
a one shot deal. Chlorophane (which means to show green)
is found in very limited quantities at Amelia Court
House, Virginia; Franklin, New Jersey and the Bluebird
Mine, Arizona, USA; Gilgit, Pakistan; Mont Saint-Hilaire,
Quebec, Canada and at Nerchinsk in the Ural Mountains,
Russia. Fluorite has other qualities besides its great
color assortments that make it a popular mineral. It
has several different crystal habits that always produce
well formed, good, clean crystals. The cube is by far
the most recognized habit of fluorite followed by the
octahedron which is believed to form at higher temperatures
than the cube. Although the cleavage of fluorite can
produce an octahedral shape and these cleaved octahedrons
are popular in rock shops the world over, the natural
(e.g. uncleaved) octahedrons are harder to find. A rarer
habit variety is the twelve sided dodecahedron however
it is never seen by itself and usually modifies the
cubic crystals by replacing the edges of the cube with
one flat face of a dodecahedron. The tetrahexahedron
is a twenty four sided habit that is also seen modifying
the cubic habit. But instead of one face replacing each
cubic edge, two faces modify the cube's edges. Occasionally
combinations of a cube, dodecahedron and tetrahexahedron
are seen producing an overall cubic crystal with no
less that three minor parallel faces replacing each
cubic edge. A fifth form is the hexoctahedron which
modifies the cube by placing six very minor faces at
each corner of the cube. Twinning is also common in
fluorite and symmetrical penetration twins, especially
from Cumberland England are much sought after by collectors.
Fluorite, as mention above, has octahedral cleavage.
This means that it has four identical directions of
cleavage and when cleaved in the right ways can produce
a perfect octahedral shape. Many thousands of octahedrons
are produced from massive or large undesirable crystals
of fluorite (hopefully!) and are sold in rock shops
and museum gift shops at a small cost. Fluorite mine
workers are reported to sit down at lunch breaks and
cleave the octahedrons for the extra cash. The octahedrons
are very popular due to their attractive colors, clarity,
"diamond-shaped" and low costs, but to a serious
collector they are nothing more than "cleavage
fragments". Fluorite not only is attractive in
its own right but is often associated with other attractive
minerals. Fluorite crystals will frequently accompany
specimens of silver gray galena, brassy yellow pyrite,
chalcopyrite or marcasite, golden barite, black sparkling
sphalerite, intricately crystallized calcite and crystal
clear quartz, even amethyst. The origin of the word
fluorite comes from the use of fluorite as a flux in
steel and aluminum processing. It was originally referred
to as fluorospar by miners and is still called that
today. Fluorite is also used as a source of fluorine
for hydrofluoric acid and fluorinated water. The element
fluorine also gets its name from fluorite, fluorines
only common mineral. Other uses of fluorite include
an uncommon use as a gemstone (low hardness and good
cleavage reduce its desirability as a gemstone), ornamental
carvings (sometimes misleadingly called Green Quartz)
and special optical uses. Fluorite is the most popular
mineral for mineral collectors in the world, second
only to quartz. Every mineral collection owned by even
the newest and youngest of mineral collectors must have
a specimen of fluorite. Fluorite is by far one of the
most beautiful and interesting minerals available on
the mineral markets. |