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21-506: The Muskeg Formation consists primarily of anhydrite , with dolomite , halite (rock salt) and limestone . The Muskeg Formation was deposited at the northern end of an embayment called the Elk Point Basin , adjacent to an extensive reef complex called the Presqu'ile Barrier . The reef had developed across the mouth of the embayment, blocking the area from the open ocean and restricting

42-421: A netted appearance and have been referred to as chicken-wire anhydrite . Nodular anhydrite occurs as replacement of gypsum in a variety of sedimentary depositional environments. Massive amounts of anhydrite occur when salt domes form a caprock . Anhydrite is 1–3% of the minerals in salt domes and is generally left as a cap at the top of the salt when the halite is removed by pore waters. The typical cap rock

63-569: A relief carving of an anhydrite kiln, made from a piece of anhydrite, for the United Sulphuric Acid Corporation . Extensive structural damage in the German city of Staufen im Breisgau has occurred since a 2007 geothermal drilling project allowed subsurface water to invade a layer of anhydrite below the city, causing extensive but uneven ground swelling as pockets of the anhydrite converted to gypsum. Molybdenite Molybdenite

84-404: A structural variety detectable by X-ray diffraction techniques. Molybdenite ores are essentially the only source for rhenium. The presence of the radioactive isotope rhenium-187 and its daughter isotope osmium -187 provides a useful geochronologic dating technique. Molybdenite is extremely soft with a metallic luster, and is superficially almost identical to graphite, to the point where it

105-427: Is a mineral of molybdenum disulfide , Mo S 2 . Similar in appearance and feel to graphite , molybdenite has a lubricating effect that is a consequence of its layered structure. The atomic structure consists of a sheet of molybdenum atoms sandwiched between sheets of sulfur atoms. The Mo-S bonds are strong, but the interaction between the sulfur atoms at the top and bottom of separate sandwich-like tri-layers

126-435: Is a salt, topped by a layer of anhydrite, topped by patches of gypsum, topped by a layer of calcite. Interaction of anhydrite with hydrocarbons at high temperature in oil fields can reduce sulfate ( SO 4 ) into hydrogen sulfide (H 2 S) with a concomitant precipitation of calcite . The process is known as thermochemical sulfate reduction (TSR). Anhydrite has been found in some igneous rocks , for example in

147-455: Is deposited if the temperature is above 40 °C (104 °F). This is one method by which the mineral has been prepared artificially and is identical with its mode of origin in nature. The mineral is common in salt basins . Anhydrite occurs in a tidal flat environment in the Persian Gulf sabkhas as massive diagenetic replacement nodules . Cross sections of these nodular masses have

168-506: Is most frequently found in evaporite deposits with gypsum; it was, for instance, first discovered in 1794 in a salt mine near Hall in Tirol . In this occurrence, depth is critical since nearer the surface anhydrite has been altered to gypsum by absorption of circulating ground water. From an aqueous solution , calcium sulfate is deposited as crystals of gypsum, but when the solution contains an excess of sodium or potassium chloride , anhydrite

189-468: Is not possible to positively distinguish between the two minerals without scientific equipment. It marks paper in much the same way as graphite. Its distinguishing feature from graphite is its higher specific gravity, as well as its tendency to occur in a matrix . Molybdenite is an important ore of molybdenum, and is the most common source of the metal. While molybdenum is rare in the Earth's crust, molybdenite

210-409: Is relatively common and easy to process, and accounts for much of the metal's economic viability. Molybdenite is purified by froth flotation , and then oxidized to form soluble molybdate . Reduction of ammonium molybdate yields pure molybdenum metal, which is used for fertilizer, as a catalyst, and in battery electrodes. By far the most common use of molybdenum is as an alloy with iron. Ferromolybdenum

231-420: Is weak, resulting in easy slippage as well as cleavage planes . Molybdenite crystallizes in the hexagonal crystal system as the common polytype 2H and also in the trigonal system as the 3R polytype. Molybdenite occurs in high temperature hydrothermal ore deposits. Its associated minerals include pyrite , chalcopyrite , quartz , anhydrite , fluorite , and scheelite . Important deposits include

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252-619: The Pine Point Formation , Presqu'ile Formation and Sulphur Point Formation . It grades into the halite-rich Prairie Evaporite Formation to the southeast through a decrease in its anhydrite content and an increase in its halite content. The porous carbonate units of the Muskeg Formation contain important oil and natural gas reservoirs in the Zama and Rainbow Lake areas of northwestern Alberta. The impermeable anhydrite and halite beds of

273-407: The intrusive dioritic pluton of El Teniente, Chile and in trachyandesite pumice erupted by El Chichón volcano, Mexico. The name anhydrite was given by A. G. Werner in 1804, because of the absence of water of crystallization, as contrasted with the presence of water in gypsum. Some obsolete names for the species are muriacite and karstenite; the former, an earlier name, being given under

294-592: The center consists of fragmental carbonate, and is overlain by the Upper Anhydrite which consists of interbedded microcrystalline anhydrite and fine- to medium-crystalline dolomite. The Bistcho Member at the top is a fragmental carbonate unit. The Muskeg Formation is disconformably overlain by the Watt Mountain Formation and conformably underlain by the Keg River Formation . It is correlated with

315-411: The chemical formulas. Distinctly developed crystals are somewhat rare, the mineral usually presenting the form of cleavage masses. The Mohs hardness is 3.5, and the specific gravity is 2.9. The color is white, sometimes greyish, bluish, or purple. On the best developed of the three cleavages, the lustre is pearly; on other surfaces it is glassy. When exposed to water, anhydrite readily transforms to

336-504: The disseminated porphyry molybdenum deposits at Questa, New Mexico and the Henderson and Climax mines in Colorado . Molybdenite also occurs in porphyry copper deposits of Arizona , Utah , and Mexico . The element rhenium is always present in molybdenite as a substitute for molybdenum, usually in the parts per million (ppm ) range, but often up to 1–2%. High rhenium content results in

357-426: The formation act to seal the reservoirs. Anhydrite Anhydrite , or anhydrous calcium sulfate , is a mineral with the chemical formula CaSO 4 . It is in the orthorhombic crystal system, with three directions of perfect cleavage parallel to the three planes of symmetry . It is not isomorphous with the orthorhombic barium ( baryte ) and strontium ( celestine ) sulfates, as might be expected from

378-563: The impression that the substance was a chloride (muriate). A peculiar variety occurring as contorted concretionary masses is known as tripe-stone, and a scaly granular variety, from Volpino , near Bergamo , in Lombardy , as vulpinite; the latter is cut and polished for ornamental purposes. A semi-transparent light blue-grey variety from Peru is referred to by the trade name angelite . The Catalyst Science Discovery Centre in Widnes, England , has

399-530: The inflow of sea water. The low water levels and excessive evaporation resulted in the deposition of anhydrite, halite and carbonate rocks . The Muskeg Formation is present in the northern half of the Elk Point Basin, in northeastern British Columbia and northwestern Alberta . It reaches a maximum reported thickness of 270 metres (890 ft). The Muskeg Formation is part of the Elk Point Group and

420-435: The more commonly occurring gypsum , (CaSO 4 ·2H 2 O) by the absorption of water. This transformation is reversible, with gypsum or calcium sulfate hemihydrate forming anhydrite by heating to around 200 °C (400 °F) under normal atmospheric conditions. Anhydrite is commonly associated with calcite , halite , and sulfides such as galena , chalcopyrite , molybdenite , and pyrite in vein deposits. Anhydrite

441-412: Was established by J. Law in 1955, based on core from a well (California Standard Steen River 2-22-117-5W6M) that was drilled north of Zama Lake. The formation is usually divided into five members. The Black Creek Member at the base consists of halite. The overlying Lower Anhydrite Member consists of microcrystalline anhydrite with minor beds of fine- to medium-crystalline dolomite. The Zama Member at

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