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The chemical formula of Borax is indicated by Na2B4O7-10H2O or Hydrated Sodium Borate. Borax is a Borate mineral. But then borate and nitrate minerals are all classified under Carbonate mineral class. This mineral commonly exhibits moderate negative relief when viewed under several adjustments on the aperture diaphragm of the petrographic polarizing light microscopes. Borax minerals are commonly found altered, at least on their surface, to the mineral Tincalconite whose chemical formula is indicated by Na2B4O7-5H2O, usually with water loss. This kind of alteration from one mineral to another is usually found leaving the original shape of the crystal. Most mineralogists usually refer to this mineral as a pseudomorph or false shape. This is because the Tincalconite mineral has the crystal shape of the predeceasing borax.

 

            The term Borax was derived from the Medieval Latin word borax, which comes from the Arabic word buraq that also comes from either the Middle Persian burak or the Persian burah. The Arabic word buraq means white. This is an allusion to the white color of the mineral specimen. Borax is also called Tincal, a Sodium Tetraborate Decahydrate. Tincal is a Sanskrit word for the mineral. The mineral Borax was first discovered at the dry lakebeds in Tibet. The Tincal that was discovered from these deposits in the 8th century was transported in ancient caravans along trade route that is now called the Silk Road. This time also indicated the first usage of Borax by the Arabian goldsmiths and silversmiths.

 

            Borax is usually found white or gray in hand sample. It is less commonly greenish or bluish. Borax is most commonly found colorless in thin section or grain mount. Borax commonly leaves a white streak after rubbing the specimen on a white porcelain streak plate. A vitreous luster is the luster that is usually exhibited by Borax in reflected light of petrographic polarizing light microscope. Borax mineral is highly water-soluble and has a slightly alkaline taste. The fracture found when Borax mineral specimen is evaluated under several adjustments on the aperture diaphragm of petrographic polarizing microscopes is usually conchoidal. The hardness measure for mineral Borax using the Mohs scale method is usually ranging from 2 to 2.5. The specific gravity measure of mineral specimen Borax usually gives an approximate value of 1.7 grams per cubic centimeters, which is commonly considered very light.

 

            Borax is commonly found as granular aggregates. Its crystals are usually stubby prisms that are often found with eight-sided cross sections. Borax crystallizes in the monoclinic system. The monoclinic system of crystal formation comprises crystals having three axes of unequal lengths. Two of which are usually found in a position that is oblique or not perpendicular to one another. However, both of which are commonly found perpendicular to the third axis. Borax mineral crystals are usually found as blocky to prismatic with a nearly square cross section, which is usually exhibiting a splendid microscope image under a polarizing light microscope for geologists. Borax can be also found in massive forms and also as crusts. Massive forms are usually found as uniformly indistinguishable crystals that are commonly found forming large masses. Borax crystals are usually found in disorganized groupings and sometimes striated. Generally, these minerals have well-formed crystals that can be found as quite large masses. Borax crystals are also brittle. Borax is also commonly associated with other interesting minerals such as halite, colemanite, calcite, hanksite, ulexite and other borates mineral.

 

            Borax has three cleavages found when it is closely evaluated with the aid of the petrographic polarizing light microscope. A single perfect cleavage is found on {100} and the two other cleavage are distinct and are found on {110} at nearly right angle position. There are simple twins found on {001} plane when the sample is evaluated under petrographic polarizing light microscope. But then these twins are rarely found. The extinction angle of Borax is about 33-degree to 36-degree measured to the trace of cleavage, and this can be seen on sections cut parallel to {010}. The fast ray vibration direction is closer to the cleavage and it is length fast. The sections that are cut parallel to {100} are found having parallel extinction with slow ray vibration direction parallel to the {110} cleavage and it is length slow. The extinction of basal sections is parallel to the trace of the {100} cleavage and it is found symmetrical to the prismatic cleavage {110}.

 

The indices of Borax do not vary significantly because there is a little compositional variation. In standard thin sections, the birefringence is found moderate and produces colors up to the lower second-order. There are some sections that do not go completely extinct and these are the ones that were cut normal to the optic axis. These sections display anomalous brown or blue interference colors and this is brought about by the strong crossed bisectrix dispersion.

 

 Sections cut parallel to {101} produces lower first-order colors.  Its optic axis dispersion is found strong while the crossed bisectrix dispersion is distinct. Isochromes are usually found having somewhat anomalous colors between crossed nicols of polarizing microscope. Borax usually have biaxial negative figure. Borax minerals are also diamagnetic. They are slightly soluble in cold water. However, they are found insoluble in acids and are very soluble in hot water. Borax also effloresces more especially on heating. It is a non-radioactive mineral. There is no specific data on the toxicity and health dangers for mineral Borax. However, Borax specimens should be treated with great care and use of sensible precaution is advised upon handling them.

 

            Borax minerals have a sweet alkaline taste. They are commonly found altering to a chalky white tincalconite with dehydration. Borax mineral crystals are usually found as white powder, which is commonly consisting of soft colorless crystals that are easily soluble in water. Borax minerals have wide variety of uses. They are commonly used as components of many detergents, enamel glazes and cosmetics. They are also used as a precursor for other boron compounds, as anti-fugal compounds for fiberglass, also as fire retardant, as an insecticide and as a flux in metallurgy. They can be also used to make buffer solutions in biochemistry. Those Borax minerals that are commercially sold are usually partially dehydrated. When Borax mineral is burned, it is commonly found producing a bright orange-colored flame. Because of this, Borax is sometimes used for homemade pyrotechnics.

 

            Borax minerals are usually found in playa lakes and other evaporite deposits. They are directly deposited in regions, specifically arid, which are from the evaporation of intermittent lakes called playas. The playas are commonly found forming only during the rainy seasons due to runoff from adjacent mountains. The runoff is usually rich in the element boron content. It is commonly found highly concentrated by evaporation in the arid climate. Because the concentration of element boron is so great, there is a formation of Borax crystals and many other boron minerals. Borax is also a salt of boric acid. Borax minerals are usually found in dry lakebeds in desert country. Borax minerals commonly occur in arid regions and are commonly found forming from the evaporation of saline lakes. They can be also produced and synthetically formed as a by-product of mining operations of borate deposits. Actually, most of the specimens from Boron, California are formed in this manner. The best field indicators of Borax mineral usually include color, crystal habit, density, locality, hardness and its wonderful association with other interesting minerals. Borax minerals notably occur at some types of localities that commonly include some areas in California, the Andes Mountains, Tibet and Turkey as well as Trona, Boron, Death Valley.



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Monday, March 24th, 2008 at 4:27 am
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The Carbonates and Borates Mineral Class
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