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The chemical formula of the mineral Boracite is indicated by Mg3B7O13Cl or Magnesium Borate Chloride. Boracite is actually a Carbonate mineral. This mineral species was named Boracite in allusion to the chemical composition of the mineral, which contains boron. Boracite minerals are commonly associated with gypsum, anhydrite, halite and some other evaporite minerals. Boracite was first described as a mineral in the year 1787. First Boracite specimens are from its type of locality of Kalkberg hill, Luneburg, Lower Saxony in Germany. In the year 1821, Sir David Brewster first observed that crystals of Boracite show double refraction when mineral crystals are examined in polarized light of petrographic polarizing light microscope. The crystals of mineral specimen Boracite are commonly found crystallizing in the orthorhombic system at low temperature and isometric at high temperature, and this can be seen clearly visible when evaluated under polarized light microscopes. In optical mineralogy, the orthorhombic crystal system comprises crystals having three mutually perpendicular axes, of which all are of different lengths. On the other hand, the isometric system when evaluated under a polarizing light microscope for geologists usually comprises crystals having three axes, all of which are perpendicular to one another and all are found equal in lengths.

 

Just like Quartz, it is known in the field of optical mineralogy that Boracite also has high temperature and low temperature phases. Cubic is the high temperature phase of Boracite. This commonly forms nice and well-shaped cubes and octahedrons, which are often modified by other isometric forms. The only phase that is considered stable at normal temperature is the low temperature orthorhombic phase. This means that after the cool down of the high temperature phase, it readily converts to the low temperature phase. The conversion process is easily accomplished and it usually does not alter the outward appearance of the mineral crystal, usually preserving isometric forms. This implies that all mineral specimens of Boracite, which are found in the collections of mineral collectors, are actually in the orthorhombic phase having the isometric formation of crystals. Almost all mineralogists refer to this as a false shape or a pseudomorph mineral. Boracite minerals are also considered evaporite. Thus, it is not really surprising to know when Boracite is found with other evaporite minerals such as gypsum, anhydrite and halite. Boracite mineral crystals are often found embedded in these other evaporite minerals. Commonly, they are found suggesting that they are formed later than others. More especially since these crystals are in the high temperature phase.

 

Boracite is actually considered as interesting borate mineral by many mineralogists in the mineral world. Boracite mineral specimanes are commonly found displaying a good fascinating color when closely evaluated with the aid of petrographic polarizing microscopes used in optical mineralogy. Boracite also shows clarity and it also possesses a significant hardness suitable for gemstone purposes. Ordinary wear dulls the surface of Boracite since it is known to be slightly soluble in water. As a mineral specimen, Boracite is considerably very attractive. Strassfurtite mineral is a known variety of Boracite in the field of optical mineralogy. This mineral variety of Boracite is in fibrous formation that is usually exhibiting majestic appearance when viewed under polarized microscope used in optical mineralogy. This Strassfurtite mineral is commonly found at Strassfurt in Germany.

 

            Almost all mineral specimens of Boracite are commonly found white to colorless in appearance in transmitted light of petrographic polarizing light microscope. They can be also found with pale tints of yellow, blue and green shades. Thin sections of mineral Boracite are commonly found colorless. Boracite commonly exhibits vitreous luster in reflected light of polarizing light microscopes for mineralogists. Sometimes they may exhibit adamantine luster in some cases described in optical mineralogy. Boracite is commonly found with absent cleavage even when evaluated under several adjustments on the aperture diaphragm of the petrographic polarizing microscope. The fracture that is most commonly found exhibited by Boracite mineral specimens are usually uneven to conchoidal that are more clearly visible when the material is examined under petrographic polarizing microscopes. In optical mineralogy, fracture describes how a mineral breaks when broken contrary to its natural cleavage planes. It can be found having very brittle fracture, which are usually found producing small and conchoidal fragments. The specific gravity measure of Boracite mineral usually gives an approximate value ranging from 2.9 grams per cubic centimeters to 3 grams per cubic centimeters, which are usually considered average for translucent minerals. The hardness measure of Boracite when it is evaluated using the Mohs scale method is commonly found ranging from 7 to 7.5. Boracite mineral commonly leaves a white streak when it is rubbed on the white porcelain streak plate.

 

            Boracite mineral crystals are commonly found transparent to translucent in appearance. Crystal habits of Boracite minerals commonly include highly modified cubes and octahedrons that are actually pseudomorphs of the high temperature isometric phase. This habit is clearly exhibited under petrographic polarizing light microscopes. They can be also found in massive forms. They can be also found in fibrous a form, which shows individual grains of long slender fibers that are commonly splendidly exhibited when viewed with the aid of polarized light microscopes. They may also appear nodular and as embedded grains, which are also exhibiting nice and interesting microscope images under polarized light microscopes. On exposure, Boracite is liable to slow alteration and is usually altered to parasite. Mineral specimens of Boracite are commonly found slightly soluble in water but are usually soluble in the hydrochloric acid. They are also found as non-fluorescent minerals. Boracite mineral specimens are known to have biaxial positive figures that can be seen clearly visible when the material is evaluated between crossed nicols of petrographic polarizing light microscope. Boracite minerals are actually found nonradioactive. Boracite is found strongly piezoelectric and pyroelectric. Boracite mineral crystals are exhibiting a rare penetration twins when evaluated between crossed nicols of geological polarizing microscope. Mineral specimens of Boracite are usually found exhibiting a moderate surface relief when it is examined under several adjustments on the aperture diaphragm of a petrographic polarizing light microscope. It also shows weak dispersion when viewed in plane light polarized microscope. There is no specific data on the toxicity and health dangers for mineral Boracite. However, mineral specimens should be treated with great care and use of sensible precaution is advised upon handling them. 

 

            The best field indicators of Boracite minerals commonly include color, lack of cleavage, crystal habit, significant high hardness and its splendid association with several other wonderful minerals. Mineral Boracite are commonly found in marine evaporates. Boracites can be found as crystals that are often embedded in the sedimentary deposits of anhydrite, halite and gypsum. Fine crystalline crystals of Boracite occurs as well-formed fine sized crystals. They may also appear as disseminated a crystal, which occurs in small, distinct particles dispersed in matrix. It has been also reported that the massive varieties of Boracite minerals are found commonly occurring as nodules in the salt-dome deposits at the Strassfurt in Germany where it has been mined as a source of boron. Boracite minerals notably occur in types of localities that usually include Bolivia, France and Yorkshire, England as well as some areas in the United States such as in Louisiana and in California.



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Thursday, August 28th, 2008 at 3:18 am
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The Carbonates and Borates Mineral Class
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