Geological Properties Of Fluorite
Geological Properties Of Fluorite, Fluorite is a very popular mineral, and it naturally occurs in all colors of the spectrum. It is one of the most varied colored minerals in the mineral kingdom, and the colors may be very intense and almost electric. Pure Fluorite is colorless; the color variations are caused by various impurities. Some colors are deeply colored, and are especially pretty in large well-formed crystals, which Fluorite often forms. Sometimes coloring is caused by hydrocarbons, which can be removed from a specimen by heating. Some dealers may apply oil treatment upon amateur Fluorite specimens to enhance luster.
Fluorite has interesting cleavage habits. The perfect cleavage parallel to the octahedral faces can sometimes be peeled off to smooth out a crystal into a perfect octahedron. Many crystals, especially larger ones, have their edges or sections chipped off because of the cleavage.
Fluorite is one of the more famous fluorescent minerals. Many specimens strongly fluoresce, in a great variation of color. In fact, the word “fluorescent” is derived from the mineral Fluorite. The name of the element fluorine is also derived from Fluorite, as Fluorite is by far the most common and well-known fluorine mineral.
Geological Properties Of Fluorite
Fluorite octahedra are often found at rock shops or gem and mineral shows. Fluorite mineral specimens have become increasingly popular due to the myriad of colors, beautiful cubic forms, and fluorescent reactions they display. The optical phenomenon of fluorescence gets its name from Fluorite. Stones come in every color of the rainbow and multi-color banding is common. Fluorite is used for gemstones, but care must be taken because it has perfect, easy cleavage in four directions. Blue John fluorite, also known as Derbystone, is a banded variety of fluorite from England that has been used for decorative objects and jewelry for centuries.
Interesting Facts:
Fluorite is fluorescent and 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 simultaneously 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.
Geological Properties Of 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.
Name Origin:
Named after its composition containing fluorine (Latin, fluere = “to flow”).
Fluorite (also called fluorspar) is the mineral form of calcium fluoride, CaF2. It belongs to the halide minerals. It crystallizes in isometric cubic habit, although octahedral and more complex isometric forms are not uncommon.
Geological Properties Of Fluorite
Fluorite is a colorful mineral, both in visible and ultraviolet light, and the stone has ornamental and lapidary uses. Industrially, fluorite is used as a flux for smelting, and in the production of certain glasses and enamels. The purest grades of fluorite are a source of fluoride for hydrofluoric acid manufacture, which is the intermediate source of most fluorine-containing fine chemicals. Optically clear transparent fluorite lenses have low dispersion, so lenses made from it exhibit less chromatic aberration, making them valuable in microscopes and telescopes. Fluorite optics are also usable in the far-ultraviolet range where conventional glasses are too absorbent for use.
What is Fluorite:
Fluorite is an important industrial mineral composed of calcium and fluorine (CaF2). It is used in a wide variety of chemical, metallurgical, and ceramic processes. Specimens with exceptional diaphaneity and color are cut into gems or used to make ornamental objects.
Fluorite is deposited in veins by hydrothermal processes. In these rocks it often occurs as a gangue mineral associated with metallic ores. Fluorite is also found in the fractures and cavities of some limestones and dolomites. It is a very common rock-forming mineral found in many parts of the world. In the mining industry, fluorite is often called “fluorspar.”
Physical Properties of Fluorite:
Fluorite is very easy to identify if you consider cleavage, hardness, and specific gravity. It is the only common mineral that has four directions of perfect cleavage, often breaking into pieces with the shape of an octahedron. It is also the mineral used for a hardness of four in the Mohs Hardness Scale. Finally, it has a specific gravity of 3.2, which is detectably higher than most other minerals.
Geological Properties Of Fluorite
Although color is not a reliable property for mineral identification, the characteristic purple, green, and yellow translucent-to-transparent appearance of fluorite is an immediate visual clue for the mineral.
Fluorescence:
In 1852, George Gabriel Stokes discovered the ability of specimens of fluorite to produce a blue glow when illuminated with light, which in his words was “beyond the violet end of the spectrum.” He called this phenomenon “fluorescence” after the mineral fluorite. The name gained wide acceptance in mineralogy, gemology, biology, optics, commercial lighting, and many other fields. (See photo pair for an example of fluorite fluorescence in tumbled stones.)
Fluorite typically glows a blue-violet color under short-wave ultraviolet and long-wave ultraviolet light. Some specimens are known to glow a cream or white color. Many specimens do not fluoresce. Fluorescence in fluorite is thought to be caused when trace amounts of yttrium, europium, samarium, or other elements substitute for calcium in the fluorite mineral structure.
Chemical Classification Halide
Color: Typically purple, green, and yellow. Also colorless, blue, red, and black.
Streak: White
Luster: Vitreous
Diaphaneity: Transparent to translucent
Cleavage: Four directions of perfect cleavage
Mohs Hardness: 4
Specific Gravity: 3.2
Diagnostic Properties: Cleavage, hardness, specific gravity, color
Chemical Composition: CaF2
Crystal System: Isometric
Uses: Numerous uses in the metallurgical, ceramics, and chemical industries. A source of fluorine, hydrofluoric acid, metallurgical flux. High-clarity pieces are used to make lenses for microscopes, telescopes, and cameras.
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