Mineral Atacamite
The chemical composition of mineral Atacamite is indicated by the formula Cu2Cl(OH)3, Copper Chloride Hydroxide. Atacamite is considered as a comparatively rare copper mineral. It belongs to the halides mineral class. The Halides group is a group of minerals that is considerably known to form the natural salts. This group also includes minerals like halite (a sodium chloride), fluorite (calcium fluoride), sal ammoniac (ammonium chloride), and sylvite (potassium chloride). Just like phosphates, Halide minerals are commonly found in evaporitic settings such as the playa lakes and landlocked seas like the Dead Sea and the Great Salt Lake. The Halides mineral group is also known to include chloride, iodide and fluoride minerals.
Atacamite is also known as a basic copper chloride mineral. Atacamite is an unusual halide mineral, which is commonly found attractive with splendid microscope views in transmitted light of geological light polarizing microscope. This Atacamite mineral is known polymorphous with two other minerals namely, paratacamite and botallackite. A polymorph mineral is a mineral that is known to share the same chemistry with other minerals but is usually found having different crystal structure when viewed with the aid of petrographic light polarizing microscope. These Atacamite, paratacamite and botallackite minerals are known members of the Oxy-halides Subclass. This Oxy-halide, a subclass of the Halides group of minerals is considered unique for they possess both oxygen and hydroxides in their chemical structures. Atacamite minerals are commonly used as mineral specimens and are considered as minor ore of copper.
Mineral Atacamite derived its name from one of the driest places in the whole world, the Atacama Desert. The Atacamite was given to the mineral species by D. de Gallizen in 1801. This mineral species Atacamite was first discovered in the year 1801 at Atacama Region in Chile. Its synonyms include Alacamite, Arsenillo, Marcylite and Kupfersand.
Atacamite mineral is commonly found in shade of deep green color in transmitted light of light polarizing microscope for geologists. This mineral is often associated with many other rare and colorful minerals such as malachite, libethenite, cuprite, linarite, cornetite, chrysocolla, caledonite, brochantite, connellite and pseudomalachite. Some of these minerals specimens can be found quite beautiful and attractive when viewed with the aid of petrographic light polarizing microscope. A combination of green, red and blue shades in one piece of specimen will certainly produce an exquisite and fascinating microscope image in transmitted light of polarized microscopes. Atacamite mineral is an interesting and wonderful piece that can be added to ones collections. This mineral is found not radioactive after chemical evaluations.
Atacamite mineral specimens are commonly found in crystals exhibiting shade of bright green, dark emerald-green to blackish green color under a petrographic light polarizing microscope. It is actually a brilliant halide mineral in splendid shades of green, which are majestically exhibited under polarizing microscopes. It is usually found displaying a vitreous luster in reflected light of polarized light microscopes. Vitreous is the luster that is commonly exhibited by a broken glass. Other guides present its luster as Adamantine, a brilliant luster that is commonly exhibited by diamonds. When Atacamite mineral specimen is rubbed on a white streak plate, it usually leaves a pale green or apple green streak. It has a perfect cleavage found in one direction when mineral specimen is viewed between crossed nicols of geological polarizing microscope. Sometimes cleavages can be found in two directions. Perfect in one direction and fair in the other. The hardness measure of mineral specimen Atacamite using the Mohs scale method is usually found ranging from 3.0 to 3.5, which is considered soft and is not suitable for gemstone purposes. The fracture found in several adjustments on the aperture diaphragm of light polarizing microscope for geologists is commonly splintery. Splintery fracture is a fracture that is commonly shown by more or less fibrous minerals. Fracture describes how a mineral breaks when broken contrary to its natural cleavage planes. Some other guides present Atacamite fracture to be conchoidal, which is a smooth curved fracture with concentric ridges of the type shown by glass. A fracture developed in brittle materials characterized by smoothly curving surfaces, just like quartz. The specific gravity measure of Atacamite gives an approximate value of 3.75g/cm³, which is considerably found above average value.
Atacamite mineral is known to crystallize in an orthorhombic system. This crystal system comprises crystals having three mutually perpendicular axes, of which all are of different lengths. The crystal habits commonly exhibited by mineral Atacamite usually include slender striated crystals that can be found in acicular to fibrous shapes, which are clearly visible when mineral specimen is viewed with the aid of geological light polarizing microscope. Acicular crystals commonly display elongated needle-like grains. Fibrous on the other hand, is a form where individual grains are long slender fibers. Crystals may also euhedral, which usually exhibits well-formed crystals showing good external forms. Sometimes crystals may appear granular, which generally occurs as anhedral to subhedral crystals in matrix. Atacamite crystals are usually vertically striated. Atacamite can be also found in fantastic association with minerals like hematite and gypsum. Atacamite mineral crystals are commonly found in transparent to translucent appearance. They are considerably brittle, a property commonly displayed by glasses and most non-metallic minerals. It is commonly found soluble in hydrochloric acid and ammonia. There are some Atacamite specimens that are found in sandy granular to compact and massive forms. These crystals are rarely twinned. Atacamite mineral is a biaxial negative figure. It has very high surface relief found between crossed nicols of petrographic light polarizing microscope. Strong dispersion is also found exhibited under polarized microscope. Atacamite mineral specimen is actually weakly pleochroic between crossed nicols of geological polarizing microscope.
Atacamite minerals commonly occur in arid regions in the upper oxidized zone of copper deposits. They are especially formed under desert saline conditions and in fumarolic deposits. They are considered as weathering product of sulphides in subsea black smoker deposits. This Atacamite mineral is actually a secondary mineral that is formed by the oxidation of other copper minerals. It is also considered as an alteration product of bronze and copper objects of antiquity. The best field indicators of Atacamite mineral commonly include color, localities, crystal habit and its fascinating and attractive association with other beautifully colored minerals. It has notable occurrences in types of localities that include Bolivia, Peru, England, Namibia and some other areas like the Mt. Vesuvius in Italy; Pinal County in Arizona, USA; the Atacama Desert in Chile; Wallaroo, South Australia; Boleo in Mexico and in USSR.
