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The chemical formula of the mineral Anglesite is indicated by PbSO4 or Lead Sulfate. Mineral Anglesite is actually a Sulfate mineral. Anglesite minerals are commonly found crystallizing in an orthorhombic crystal system. In optical mineralogy, this crystal system comprises crystals having three mutually perpendicular axes, of which all are of different lengths. In the year 1783, Dr. Withering the first to recognize Anglesite as a mineral species. It was him who actually discovered the new species in the Parys Copper Mine in Anglesey Island. The new mineral species is named Anglesite after its original type of locality, the Island of Anglesey, Wales, an island found at the northern tip of United Kingdom. The name was actually given by F.S. Beudant in the year 1832.  These minerals species has crystals, which are small in size and simple in form, are formerly found abundantly on a matrix of dull limonite. The most popular and attractive variety of Anglesite minerals is the specimen that commonly exhibits yellow shade in transmitted light of polarizing light microscope. This mineral Anglesite, which is also known as lead mineral, is usually formed in the oxidation zones of the lead sulfide ore galena.

 

            Crystals of Anglesite mineral usually vary from being transparent to being translucent in appearance. It can be also found occuring in earthy masses.  Anglesite crystals may appear bladed or tabular when viewed closely under a petrographic polarizing microscope. It is also usually found dominated by two large faces of a pinacoid at the top and at the bottom, and small faces of a prism usually found forming a jutting angle on every side. The variety of combinations and habits presented by the crystals of mineral Anglesite when it is viewed with the aid of polarizing microscopes for mineralogists is very extensive. There can be several variations on dominating faces and different complex forms may occur. There have been nearly two hundred distinct forms being figure by V. Von Lang in his monograph of the Anglesite mineral species.

 Mineral Anglesite usually exhibit a typical high luster when closely evaluated in reflected light of polarizing microscope used in optical mineralogy, and this is commonly associated with lead minerals. Anglesite minerals usually appear in shades of white, yellow, green, pale gray, and blue when evaluated under petrographic polarizing microscope. Mineral Anglesite in thin sections are usually colorless. As described in optical mineralogy, they may also appear in colorless crystal if they are pure. One of the significant findings in the field of optical mineralogy is the fact that colorless crystals commonly allow the whole constituents of a white light to pass through making the specimen non-pleochroic even between crossed nicols of polarized microscopes. Anglesite is most commonly found exhibiting a high adamantine luster when viewed in reflected light of polarizing light microscope used in optical mineralogy. It is a brilliant luster that is commonly exhibited by diamonds and cerussite. The hardness measure of mineral Anglesite when it is evaluated using the Mohs scale method is usually found ranging from 2.5 to 3.0. The cleavage found exhibited by mineral Anglesite is usually in three directions. With the aid of a polarizing light microscope for mineralogists, a perfect cleavage can be found in one direction and a less perfect one in the other two directions. The specific gravity measure of Anglesite mineral specimen actually gives an approximate value of 6.3 grams per cubic centimeters, which is considered very heavy for translucent minerals. This heaviness of the mineral Anglesite is usually due to its lead content. When this mineral specimen is rubbed on a white streak plate, it commonly shows white streak. Gray colored specimens on the other hand, shows pale yellow streak. 

This Anglesite mineral is usually associated with other minerals like limonite, galena, barite, and cerussite. The index of refraction of mineral Anglesite is usually very high at about 1.88. Some Anglesite mineral specimens may exhibit fluoresce yellow under ultraviolet light. Anglesite mineral is commonly found having a biaxial positive figure when evaluated between crossed nicols of petrographic polarizing microscopes. It shows relatively strong dispersion when viewed in plane light of polarizing light microscope for geologists. This mineral is chemically non-radioactive.

 

            Anglesite is a mineral of secondary origin. It is commonly found in the upper, oxidized portions of lead veins. They are commonly formed in veins, oxidation zones, evaporitic deposits, and in contact metamorphic zones. It also occurs as an oxidation product of primary lead sulfide ore called galena. At most localities, Anglesite is found as isolated crystals in the lead-bearing ore. Specimens of this mineral Anglesite can be found in type of localities that includes Anglesey, Wales; Derbyshire, England; Chihuahua, Mexico; Toussit, Morocco; Phoenixville, Pennsylvania; Austria and Tsumeb, Nambia.



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Tuesday, July 29th, 2008 at 7:26 am
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The Sulfates Mineral Class
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