The chemical formula of mineral Enargite is indicated by Cu3AsS4 or Copper Arsenic Sulfide. Enargite is actually a Sulfide mineral. The name Enargite was derived from the Greek word enargos, which means distinct. This is an allusion to its distinct habit from its nearly perfect prismatic cleavage. Enargite was originally described as a new species from the copper mines of the San Francisco vein, Junin Department, Peru. Enargite mineral is also found soluble in nitric acid and aqua regia. The first discovery of the mineral is in the year 1850. Enargite is known to crystallize in the orthorhombic system of crystal formation. In optical mineralogy, this orthorhombic crystal system comprises crystals having three mutually perpendicular axes, of which all are of different lengths. The symmetry of mineral Enargite however is very uncommon. Enargite belongs to the class of symmetry that produces crystals which are hemimorphic and classified as hemimorphite. In optical mineralogy, the hemi means half, the morph means shape. Thus, hemimorphic crystals are found having differently shaped tops compared to the bottom crystals. Enargite crystals are typically found with flat face. This is because Enargite crystals do not have any unique terminations. Even the bottoms of the crystals have a flat face as well. In the hemimorphite crystals, the top termination faces are actually positioned slant to a point and the bottom termination is much more blunted, a clear difference. But then because of the crystal form of the mineral Enargite, its hemimorphic character is unfortunately undetectable.
Enargite is considered as a minor ore of copper and it is most commonly found exhibiting interesting and wonderful microscope images when viewed with the aid of an ore polarizing microscope. Enargite is also commonly used as mineral specimen and it is often found showing splendid images under petrographic polarizing microscopes used in optical mineralogy. Enargite is somewhat a rare copper mineral. It does not often form well-shaped crystals but then there some fine Enargite clusters that can be found from several localities. The tabular to blocky to prismatic forms Enargite crystals are usually found pseudohexagonal or having six sides but not identical and this can be found more clearly exhibited when examined with the aid of polarizing microscopes for mineralogist or the ones used in optical mineralogy. Twinning can be also found displayed by the mineral when it is evaluated with the aid of polarized light microscopes for geologists. The twinned crystals of Enargite usually form nice star shaped cyclic twin called trillings that is commonly clearly visible when the mineral is evaluated with the aid of geological polarizing light microscopes.
Enargite is commonly found displaying gray to black color when viewed closely with the aid of petrographic polarizing microscopes. Enargite is most commonly found exhibiting a metallic luster in reflected light of polarizing microscopes used in optical mineralogy. Enargite is also most commonly found showing a prismatic perfect cleavage in two directions when closely evaluated under polarizing microscope. There is another distinct cleavage in two other directions that are also prismatic but with different orientations. Enargite is usually found showing uneven fracture when viewed under polarizing microscope used in optical mineralogy. The specific gravity measure of the mineral is usually found as an approximate value of 4.4+ grams per cubic centimeters, which is considered average for metallic minerals. The hardness measure of mineral Enargite when it is evaluated using the Mohs scale method is usually ranging from 3 to 3.5. Enargite mineral crystals are usually found brittle. Enargite mineral is non-fluorescent in any wave of the ultra violet light. Enargite is most commonly found leaving a black streak when mineral section is rubbed on a white porcelain streak plate.
Most Enargite crystals are found opaque in appearance. The crystal habit of Enargite as described in optical mineralogy usually include pseudohexagonal prismatic to blocky or tabular crystals that are often terminated by a flat pedion face which can be also seen clearly visible when the mineral is viewed with the aid of petrographic polarizing microscope. Some Enargite mineral crystals can be also found massive, granular and in radiating aggregates when can be more splendidly wonderful when viewed under polarized light microscopes used in optical mineralogy. Twinning can be also found common in Enargite crystals. Sometimes it results in a star shaped cyclic twin called a trilling that can be more fascinatingly wonderful when viewed under petrographic polarizing light microscopes for mineralogists.
Enargite is an anisotropic mineral. In optical mineralogy, this means that it consequently appear alternately dark and illuminated when viewed at different angles between crossed nicols of petrographic polarizing microscope. Enargite usually appears gray to light pinkish brown with deep red internal reflection when evaluated in plane-polarized light of geological polarizing microscopes. Enargite is also found weakly pleochroic when closely evaluated under polarizing microscopes for mineralogists. There is no specific data found on the toxicity and health dangers for mineral Enargite. However, the specimens of the mineral should be treated with great care and use of sensible precaution is advised upon handling them. This mineral is nonmagnetic. Enargite is also a non-radioactive mineral.
Enargite is commonly associated with other interesting minerals like bornite, pyrite, sphalerite, chalcocite, galena, tennantite, quartz, chalcopyrite, covelite and other sulfide minerals. The best field indicators of mineral Enargite usually include crystal habit, cleavage, streak and association. Enargite minerals can be found in medium-temperature ore veins. It can be also found forming in the hydrothermal replacement deposits. Enargite is actually a late stage mineral in low temperature deposits. Mineral Enargite notably occurs at some famous locality including Butte, Montana, San Juan Mountains, Colorado and at both Bingham Canyon and Tintic, Utah in the United States. It can be also found as Sonora in Mexico, in the Islands of Luzon in the Philippines, in Morococha and Cerro de Pasco in Peru and also in Argentina and Chile.
