Mineral Boulangerite
The chemical composition of the mineral Boulangerite is indicated by the formula Pb5Sb4S11, a Lead Antimony Sulfide. This Boulangerite belongs to the Sulfides and Sulfosalts mineral class. The Sulfides class comprises minerals, which are composed of various metals combined with the element sulfur. The minerals, which belong to this class, are considered economically important as metal ores. This mineral class commonly includes galena, a lead sulfide; sphalerite; and many other minerals such as chalcopyrite, a copper iron sulfide; pyrite, an iron sulfide that is commonly known as fool’s gold; and pentlandite, a nickel iron sulfide. Sulfides are considered as one of the major ore of important metals like silver, lead, gold, and copper. Sulfide ore mineral samples are commonly evaluated under an ore polarizing light microscope. This mineral class usually possesses strong generalities. Majority of the minerals that belongs to the Sulfides class are opaque in appearance, exhibiting a metallic luster in reflected light of petrographic polarizing light microscope, with hardness ranging from soft to average, also considered generally sectile, with high specific gravities, usually exhibiting black or dark colored streaks when specimens are rubbed on a white porcelain streak plate, and commonly found igneous in origin. Only few members of this class exhibits vitreous luster or transparent in appearance. Orpiment is one of this, which tends to break the mold.
Boulangerite mineral is considered as one of the few sulfide minerals. Boulangerite is commonly found in forms of fine acicular crystals, which usually appear as hair like fibers when viewed under a geological microscope. Sometimes a mineral specimen can be seen covered with hair like fibers due to the fibrous aggregates of Boulangerite that are usually found so thick. It can be also found sparsely disseminated between other minerals and sometimes it can be confused with actual hairs or dark lint. There are two other sulfide minerals, which are usually found forming similar acicular crystals. These sulfide minerals are the Jamesonite and the Millerite. These two minerals can be actually mistaken for Boulangerite. However, they can be distinguished from Boulangerite through the yellow color that is commonly displayed by millerite and the brittleness of the jamesonite crystals.
Boulangerite minerals are also considered members of the sulfosalt. Sulfosalts are segments of the sulfides mineral class where the antimony content acts more like a metal rather than a non-metal. And it is commonly found occupying the position where it is usually bonded to sulfurs. It has been also known that jamesonite and also Boulangerite have been called as feather ores. Mineral Plumosite, a variety of Boulangerite was named that way due to its crystal habit, which is usually plumose or feathery. It was actually been thought to be a different mineral. Boulangerite minerals are commonly used as minor ores of lead. Boulangerite ore minerals are actually fascinating to view under an ore polarizing light microscope. Boulangerite are also used as mineral specimens.
Boulangerite mineral is considered as one of the few sulfide minerals. This mineral species Boulangerite was first discovered in the year 1837 in France. Boulangerite mineral was actually named after Charles L. Boulanger (1810-1849), a French mining engineer.
Boulangerite minerals are usually found in shades of blue lead gray to gray in reflected light of geological microscope. The luster that is often found exhibited by Boulangerite in reflected light of petrographic polarizing light microscope is either metallic or silky. When Boulangerite mineral specimen is evaluated between crossed nicols of polarizing light of a geological microscope, it commonly displays a good cleavage in one direction that is parallel to the length. The fracture found under several adjustments on the aperture diaphragm of polarizing light microscope for geologists is commonly uneven. The fracture actually describes how a mineral breaks when broken contrary to its natural cleavage planes. The hardness measure of Boulangerite mineral using the Mohs scale method is usually found as 2.5. When Boulangerite mineral specimens are rubbed on the white streak plate, they are usually found leaving a gray to brown streak. The specific gravity measure of mineral specimen Boulangerite is commonly found in values ranging from 5.8g/cm³ to 6.2g/cm³, which is commonly considered heavier that average for metallic minerals.
Boulangerite minerals are commonly known to crystallize in the monoclinic system, which can be seen clearly when specimen is evaluated with the aid of polarized light microscope for geologists. 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. Boulangerite crystals are commonly found opaque in appearance. The crystal habits of Boulangerite minerals usually include dense or sparse felted masses of acicular crystals that can be made clearly visible with the aid of polarizing microscope for geologists. Acicular crystal habit occurs as needle like crystals. They can be also found in fibrous forms, which are interesting to view under polarized light microscope. They may actually appear in massive fibrous crystals, which are distinctly fibrous fine-grained forms. Sometimes, they can be also found in form of compact plumose or feathery masses that are usually displaying fascinating microscope images under petrographic polarizing microscopes. Plumose or mica like minerals usually forms aggregates of plume-like crystals. Boulangerite crystals are also brittle, a property that is commonly displayed by glasses and most non-metallic minerals. Boulangerite minerals are commonly associated with several interesting minerals that include galena, pyrite, arsenopyrite, siderite, quartz and sphalerite.
Boulangerite mineral is found to be distinctly anisotropic between crossed nicols of petrographic polarizing light microscope. When Boulangerite mineral specimen is evaluated in polarizing light microscope for geologists, it is usually found weakly pleochroic. Boulangerite crystals are considered very flexible. Boulangerite minerals do not react with cold weak acids. But they are commonly found easily dissolved in hot strong acids. They also fuse very easily. Boulangerite mineral specimens are not magnetic. They are also found as not radioactive minerals after several chemical evaluations.
Boulangerite minerals are commonly formed in medium and low temperature ore deposits. They are commonly found in hydrothermal veins. They can be also found present in lead ore deposits. The best field indicators of Boulangerite commonly include color, flexibility, crystal habit, luster, and its fascinating association with several other interesting minerals. Boulangerite minerals notably occur at some types of localities including several areas in the United States such as Colorado, Nevada, Washington, Idaho and Montana as well as several other localities like Mexico, China, Germany, Pribram, Trepca and Sweden.
