Hydrogen Minerals
by John Betterton
Hydrogen is the fist element of the periodic Table and is the most plentiful element in the Universe. Its crustal abundance is 0.15% and is mainly present as water. World production is around 40 million tonnes per annum with almost limitless reserves...
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and is mostly produced from natural gas. North America and Europe are large producers of hydrogen. It is used to produce water, hydrochloric acid, ammonia, fertilizers, paints, foods, chemicals, bulk organic compounds, in welding, metallic ore reduction, cryogenics and hydrogen fuel cells etc. The majority of minerals contain this element in the form of water, H2O and or hydroxide, OH, or simply as H in all mineral classes except sulphides and sulphosalts. We only deal with those minerals that contain the most hydrogen in their formulae.
Ice,
H2O, is not commonly thought as a mineral but does possess the necessary characteristics of one. It is hexagonal and forms prismatic crystals (as snow) to about 0.5 m in size. Frequent forms include stellate, skeletal, flattened, rounded and concentrically zoned crystals, stalactitic, compact, massive, as frost, columnar, arborescent and feathery habits on the surface of the Earth. Twinning is abundant.
The mineral is transparent to translucent and has a vitreous lustre. It is colourless, white from inclusions, pale blue to pale green in thick deposits. The streak is white with a conchoidal fracture. It is brittle with a hardness of 1.5. The specific gravity is very low at 0.9. It is a liquid above 0 ° C and is diamagnetic in character. The above properties together with its mode of occurrence are enough for certain identification. It forms at low temperatures by sublimation in the atmosphere and in layers over open bodies of water (oceans, seas, rivers, streams, lakes ponds etc), in glaciers and develops very thick masses, especially in polar icecaps. Ice is of worldwide distribution and is found in most Countries. Some noted examples for ice are from Canada, USA, Russia, Denmark, and Antarctica etc and from numerous mountain regions of most countries.
Gibbsite,
Al(OH)3, is the most widespread polymorphs of Al(OH)3. It is a typical product of weathering of aluminous minerals and is abundant in bauxite deposits, lateritic soils, low temperature hydrothermal veins and in metamorphic environments. It is associated with diaspore, bohmite, corundum, kaolinite, goethite and quartz etc. Gibbsite crystallises in the monoclinic system forming pseudohexagonal tabular crystals with varied twinning. Also present as lamellar, acicular, stalactitic, mammillary and compact earthy habits. It is colourless, white, grey, pale green and pale red in colour with a vitreous, pearly to dull lustre.
The mineral is transparent with a perfect cleavage and is tough. Its specific gravity is 2.4. It has a strong argillaceous odour when breathed upon. Optical properties and xray methods are helpful for identification.
A few gibbsite locations for specimens can be found in Australia, Austria, Brazil, Canada, China, Germany, Greece, Hungary, Italy, Jamaica, Norway, Russia and the USA.
Antarcticite,
CaCl2.6H2O, is a trigonal mineral that forms aggregates of acicular crystals up to 15 cm with generally poor quality terminations. It is colourless with a vitreous lustre. It possesses perfect and good cleavages and is brittle. The hardness is between 2 and 3 and is highly hydroscopic. Specific gravity is low at 1.7. Chemistry, physical properties and environment are important for characterisation. Antarcticite occurs as a precipitate from highly saline brines under very arid conditions, in stratified fresh to brackish salt-water columns in onshore “blue holes” near islands and in inclusions in zoned mafic pegmatoid rocks. It is associated with halite, gypsum, celestine and quartz. Samples have been obtained from Antarctica, USA, South Africa and Russia.
Natron,
Na2CO3.10H2O, is a colourless to white mineral and may be tinted yellow or grey due to impurities with a vitreous lustre. It is translucent with distinct and imperfect cleavages. This species has a conchoidal fracture and is brittle. Its hardness is very low at 1-1.5 and the specific gravity is also low at 1.4.
Natron is soluble in water with an alkaline taste and dehydrates rapidly in air to thermonatrite. It is found as granular to fine crystalline aggregates forming crusts, efflorescences and coatings. This mineral is monoclinic. Chemistry, physical properties and mode of occurrence help in distinguishing this carbonate. It occurs on margins of soda-rich lakes, lake bottoms, efflorescences on lavas and in alkaline massifs. Accompanied species are thermonatrite, trona, mirabilite, gaylussite, gypsum and calcite. Confirmed occurrences are in Austria, Italy, Hungary, Russia, China, USA, Canada, Australia, and Bolivia.
Inderite,
MgB3O3(OH)5.5H2O, is a relatively uncommon primary mineral in lacustrine borate deposits associated with hydroboracite, kurnakovite, borax, ulexite, orpiment and realgar. It is monoclinic and develops long prismatic crystals with near square cross-sections to over 30 cm in size, with a variety of different habits. It also occurs as aggregates of minute needles, reniform, nodular and massive forms. This mineral is colourless to white in colour with vitreous, pearly, greasy to dull lustre. It has perfect to good cleavages and its hardness is 3. The specific gravity is 1.8 and is transparent to translucent. Above properties, chemistry and occurrence contribute in recognition. Inderite specimens may be collected in countries like the USA (large crystals in California!), Argentina, Kazakhstan, Turkey and China.
Struvite,
(NH4)Mg(PO4).6H2O, crystallises in the orthorhombic system as equant, wedge-like short prismatic or tabular crystals which may be hemimorphic. Twinning is present and a varied crystallography is apparent. It is transparent to translucent and is colourless with tinted yellow or brown shades from impurities. The mineral has a vitreous lustre and is slightly soluble in water, dehydrates in dry warm air. It has good to poor cleavages with a subconchoidal to uneven fracture. This mineral is pyroelectric and piezoelectric in character. The hardness is 2 and the specific gravity is 1.7. The above properties, chemistry and occurrence help in identification purposes. Struvite is formed in bird or bat guano in caves and surfaces deposits with newberyite, hannayite, brushite and stercorite. Samples have been acquired from sites in South Africa, Malaysia, Namibia, Australia, USA, Canada and some other lesser countries.
Chaclophyllite,
Cu18Al2(AsO4)4(SO4)3(OH)24.36H2O is a very desirable arsenate mineral that is emerald-green, grass-green, bluish green to blue in colour with a vitreous to subadamantine lustre. It has a pale green to bluish green streak. This species is transparent to translucent. It possesses a perfect and micaceous cleavages with a hardness of 2. The specific gravity is 2.6.
Chalcophyllite is hexagonal and hexagonal crystals to about 1 cm in size. Flattened, striated and triangular habits occur along with numerous other habits.
Rosettes, drusy and foliated massive forms also are found.
Twinning is present and probably is universal. Crystal habit, colour, chemistry and occurrence help in its identification. It is a rare secondary mineral developing in oxidised arsenate zones in hydrothermal polymetallic deposits. Associated species include some of the following, azurite, malachite, brochantite, chrysocolla, spangolite, connellite, cuprite, cyanotrichite, strashimirite, parnauite, lavendulan, langite, clinoclase, pharmacosiderite, bayldonite, arsenopyrite, goethite and quartz etc.
Numerous locations are known for this species. Some are located in England (large crystals), Germany, USA, Slovakia, Chile, Czech Republic, France, Austria and in Italy.
Alunogen,
Al2(SO4)3.17H2O, is formed by reaction of sulphates from decomposing aluminous minerals in shales, slates, gossans, altered wall rocks in pyritic deposits, in coal seams and in lowtemperature fumaroles.
Pyrite, marcasite, halotrichite, pickeringite, epsomite, alum, melanterite and gypsum accompany alunogen. It crystallises in the triclinic system with rarely formed thin platy or prismatic crystals, some with a six-sides. Up to 60 crystal habits have been described for this mineral. It also occurs as delicate masses, crusts and efflorescences. This species is colourless, white or pale yellow to red from impurities with a vitreous to silky lustre. It is transparent with a perfect cleavage and a low hardness of 1.5-2. The specific gravity is low at 1.7 and is soluble in water with alum-like acid sharp taste.
Geological environment, physical, chemical properties help towards characterisation.
This species is quite common with many differently described locations worldwide.
Specimens come from Slovakia, Italy, France, Spain, Germany, Austria, Russia, Czech Republic, Hungary, Romania, Chile, USA, Canada, China, Antarctica, Australia and New Zealand.
Faujasite-Na,
(Na2,Ca,Mg)3.5[Al7Si17O48].32H2O, is a member of the faujasite series of the large Zeolite group. It is cubic with typical octahededral or uncommonly trisoctahedral crystals. Twinning is common. The mineral is colourless, white or brown with a white streak. It has a vitreous to adamantine lustre and a perfect cleavage. The fracture is uneven to conchoidal in form. It has a distinctive octahedral crystal form, but x-rays and chemistry are required for certain identification.
Faujasite-Na is rare in vesicles of basalts, phonolites and tuffs. It is associated with other zeolites (such as phillipsites, offretite and chabazites), olivine series, augite and nepheline. Display specimens are not known, but micro-crystals are readily available from the Sasbach location in Baden-Wurttemberg, Germany. Other sites include those in Aci Castello, Catania Province, Sicily, Italy; Mont Saint-Hilaire, Quebec, Canada; several locations around Safawi, Jordan; and Kalepa Ridge, Kauai Island, Hawaii, USA.
Fluorine and its minerals will be the next element for discussion.
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