Mineral Arthurite
The chemical composition of mineral Arthurite is indicated by the formula CuFe2(AsO4,PO4,SO4)2-4H2O, Hydrated Copper Iron Arsenate Phosphate Sulfate Hydroxide. This Arthurite belongs to the Phosphate mineral class. The Phosphates group of minerals commonly includes all minerals having a tetrahedral unit indicated by the formula AO4 with a negative three charge, where A can stand to be either antimony, arsenic, phosphorus or vanadium. The basic tetrahedral unit can be combined with other metal ions on a one to one ratio. Usually, it can be found in a more complex combinations with other ions such as the hydroxide groups with formula indicated by (OH), the uranyl groups with formula indicated by (UO2), a halogen or even water molecules. Apatite mineral is the most common phosphate, of which it is considered as an important biological mineral that is commonly found present in the teeth and bones of many animals. A typical phosphate mineral usually exhibits vitreous to dull luster in reflected light of polarizing microscope. Phosphate mineral specimens are often found strongly colored with density measure that is usually above average. The index of refraction found between crossed nicols of geological light polarizing microscope is usually low. The hardness found for most phosphate minerals is commonly at an average ranging from 4 to 7. Some other characteristics and properties vary for each kind of mineral.
Arthurite mineral is actually considered as a rare copper iron arsenate. Arthurite specimens that are much sought after are usually the ones, which are usually found from the classic mines of Cornwall, England that are often associated with other rare minerals such as beudantite and pharmacosiderite. Arthurite mineral is usually considered as unusual mineral because in its chemical structure, it can found that variety of anions are contained such as sulfate, arsenate, and phosphate. It can be noticed that the arsenate anion usually dominates in natural specimens, but it can be also found that all anions are usually present in the same specimen.
This mineral species Arthurite is a known member of the so-called Arthurite group where this mineral lends its name. This Arthurite group of minerals is a small group, which is comprised of rather obscure minerals. This group is actually popular having a general formula indicated by XFe2(AO4)2(O,OH)2-2H2O, a hydrated iron arsenates and phosphates where X can stand as either manganese, iron, copper, and/or zinc. The A in the formula can stand as either phosphorous or arsenic. This group is generally monoclinic. Its members are the Arthurite, a Hydrated Copper Iron Arsenate Phosphate Sulfate Hydroxide; the Earlshannonite, a Hydrated Manganese Iron Phosphate Hydroxide; the Ojuelaite, a Hydrated Zinc Iron Arsenate Hydroxide and the Whitmoreite, a Hydrated Iron Phosphate Hydroxide.
The new mineral species Arthurite was named after Sir Arthur Edward Ian Montagu Russell (1878–1964) and Mr. Arthur William Gerald Kingsbury (1906–1968), both of which are English mineralogists and mineral collectors. This is in honor for their contributions to British mineralogy. Arthurite mineral was first discovered in the year 1964 at Hingston Down Consols, Gunnislake Area, Callington District at Cornwall, England, United Kingdom.
Arthurite mineral specimens are commonly found in shades of apple green to emerald green and sometimes in pale olive-green in transmitted light of petrographic light polarizing microscope. These minerals usually exhibits splendid microscope image in polarized light of geological light polarizing microscopes. The cleavage lines of Arthurite are not observed even between crossed nicols of geological light polarizing microscope. They are actually found having an absent cleavage even several adjustments on the aperture diaphragm of the polarized microscope is made. It has uneven fracture when specimen is evaluated under a petrographic light polarizing microscope. Uneven and flat surfaces are found, which are fractured in uneven in an uneven pattern. Fracture describes how a mineral breaks when broken contrary to its natural cleavage planes. Arthurite are actually considered brittle, a property that is generally displayed by glasses and most non-metallic minerals. The hardness measure of Arthurite using the Mohs scale method is usually ranging from 3 to 4, which is not really considered suitable for gemstone purposes. It commonly exhibits vitreous to pearly luster in reflected light of polarized microscopes. The specific gravity measured for the Arthurite specimen is commonly at an approximate value ranging from 3.0g/cm³ to 3.2g/cm³, which is commonly considered as average for translucent minerals. When mineral specimen is rubbed on a white streak plate, it usually leaves a green streak. Arthurite minerals are commonly found having either positive or negative biaxial figure between crossed nicols of polarized light microscope. It shows high surface relief under several adjustments on the aperture diaphragm of polarizing microscopes. Arthurite is pleochroic on various shades of green.
Arthurite mineral specimens are commonly found having typical green colored crystals. These crystals are usually translucent in appearance. They may also appear transparent at some time. Arthurite minerals are known to crystallize in a 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. Crystal habits of Arthurite are commonly found to include prismatic crystals, where crystals forms appear in shape like slender prisms in transmitted light of polarizing microscopes. They commonly form small acicular crystals, which have splendid microscope views in transmitted light of light polarizing microscope. Acicular habit usually occurs as needle-like crystals. Some other crystal habits like globular aggregates can be also found exhibited by Arthurite crystals. Crystals may also appear in spherical, rounded aggregates. They may even be found in crusts forms. Arthurite minerals are usually associated with other minerals such as pharmacosiderite, beudantite, and other secondary arsenate minerals. There is no specific data on toxicity and health dangers for mineral Arthurite. However, this mineral should also be treated with great care and use of sensible precautions upon handling them. This mineral Arthurite is chemically evaluated and found to be not radioactive.
The best field indicators of Arthurite mineral usually include its color, streak, crystal habits and its remarkable associations with other minerals. Arthurite mineral is commonly formed as secondary mineral in the oxidation zones of some copper deposits. They are actually formed by the alteration of arsenopyrite or enargite. It has notable occurrences in types of localities like Atacama Province, Chile; Calstock, Cornwall, England; and Majuba Hill, Nevada in the United States.
