Minerals isometric

If dp is the mean projected diameter, the mean projected area is nd2/4 and the volume is k d2, where k is a constant whose value depends on the shape of the particle. For a spherical particle, k is equal to tt/6. For rounded isometric particles, that is particles in which the dimension in three mutually perpendicular directions is approximately the same, k is about 0.5, and for angular particles k is about 0.4. For most minerals k lies between 0.2 and 0.5. 

If the diffusion medium is isotropic in terms of diffusion, meaning that diffusion coefficient does not depend on direction in the medium, it is called diffusion in an isotropic medium. Otherwise, it is referred to as diffusion in an anisotropic medium. Isotropic diffusion medium includes gas, liquid (such as aqueous solution and silicate melts), glass, and crystalline phases with isometric symmetry (such as spinel and garnet). Anisotropic diffusion medium includes crystalline phases with lower than isometric symmetry. That is, most minerals are diffu-sionally anisotropic. An isotropic medium in terms of diffusion may not be an isotropic medium in terms of other properties. For example, cubic crystals are not isotropic in terms of elastic properties. The diffusion equations that have been presented so far (Equations 3-7 to 3-10) are all for isotropic diffusion medium. 

Although the correlation between ionic porosity and diffusivity is imperfect, there is a rough trend that oxygen diffusivity in the minerals increases with increasing IP. The trend is useful in qualitative estimation of closure temperature (among other applications). Extending the relation to metallic systems, one prediction is that diffusion in face-centered cubic structure (25.95% free space) is slower that that in body-centered structure (31.98% free space) of the same metal composition. To avoid the issue of anisotropy, it would be worthwhile to reexamine the relations between diffusivity and ionic porosity using only isometric minerals. 

ANALCIME. A common zeolite mineral, NaAlSi2C>6 H20, a hydrous soda-aluminum silicate. It crystallizes in the isometric system, hairiness, 5-5.5 specific gravity, 2.2. vitreous luster colorless to white but may be grayish, greenish, yellowish, or reddish. Its trapezohedral crystal resembles garnet but is softer it is distinguished from lcucitc only by chemical tests. 

Argentite is probably die most important primary silver mineral. However, it maintains its cubic (isometric) characteristic only above 179 C (354°F). Upon cooling, the inward structure inverts to a noil-isometric form, usually orthorhombic, yet retaining its original outward form. It is, therefore, a paramorph after argentite, known as acanthite. 

CUPRITE. The mineral cuprite, cuprous oxide. Cu 0. occurs as isometric crystals, usually octahedrons, hut may he cubes, dodecahedrons or modified combinations, it also is found as a massive, earthy material. Its fracture is conchoidal to uneven brittle hardness,, 1.5-4 specific gravity, 6.14 luster, submetallic to earthy color, red nearly transparent to nearly opaque. Its streak is shining brownish-red. Cuprite is a secondary mineral resulting doubtless from the oxidation of copper sulfides. It is often found associated with native copper, malachite and azurile. 

FLUORITE. Fluorite is a calcium fluoride mineral CaFi crystallizing in the isometric system, often in superb cubic crystals. Twinned crystals are common, usually as cubic penetration twins. It is found in many diverse... 

HESSITE. A mineral telluride of silver. AgyTe. with some gold, crystallizing in the monoclinic syslem at normal temperatures isometric system above I49.5F (65.3 C). Crystalline form not ohvious at normal temperatures. Hardness. 2-3 specific gravity. 8.24-8.45 color, gray with metallic luster opaque. Named after G.H. Hess (1802— 1850). 

PEROVSKITE. The mineral perovskite is calcium titanate, essentially CaTiCL, with rare earths, principally cerium, proxying for Ca, as do both ferrous iron and sodium, and with colunibiuni substituting for titanium, ll crystallizes in die orthorhombic system, but witli pseudo-isometric character fracture subconchoidal to uneven brittle hardness, 5.5 specific gravity. 4 luster, adamantine color, various shades of yellow to reddish-brown or nearly black transparent to opaque. It is found associated with chlorite or serpentine rocks occurring in the Urals, Baden, Switzerland, and Italy, It was named for Von Perovski. 

SPERRYLITE. A mineral diarsenide of platinum. PtAs2. Crystallizes in the isometric system. Hardness, 6-7 specific gravity, 10.58 color, white opaque. Named after Francis L, Sperry, Sndbury, Ontario. 

SPHALERITE BLENDE. Also known as zinc blende, this mineral is zinc sulfide, tZn, Fc)S, practically always containing some iron, crystallizing in the isometric system frequently as tetrahedrons, sometimes as cubes or dodecahedrons, but usually massive with easy cleavage, which is dodecahedral. It is a brittle mineral with a conchoidal fracture hardness, 2.5-4 specific gravity, 3.9-4.1 luster, adamantine to resinous, commonly the latter. It is usually some shade of yellow brown or brownish-black, less often red, green, whitish, or colorless streak, yellowish or brownish, sometimes white transparent to translucent. Certain varieties... 

SYLVITEA. A mineral, potassium chloride, KC1, occurring in cubes, or as cubes modified by octahedra. Sylvite is therefore isometric. It has a perfect cubic cleavage uneven fracture is brittle hardness. 2 specific gravity, 1.9 luster, vitreous colorless when pure but may be white, bluish, yellowish or reddish due to impurities. It is soluble in water. It is much rarer than halite and has been found as sublimates at Mt. Vesuvius and as bedded deposits al Slassfurl, Genii any. Extensive deposits occur in sedimentary deposits in the Permian basin of southwestern New Mexico, near Carlsbad, in die United States. 

The dimorphs pyrite (FeS2) and marcasite (FeS2) are the dominant sulfide minerals in coal pyrite is the more abundant. Pyrite and marcasite have different crystal forms pyrite is isometric and marcasite is orthorhombic. These two minerals are readily observed and, to some degree, easily removed as well as being especially interesting because they contribute significantly to the total sulfur content that causes boiler tube fouling, corrosion, and pollution by emission of sulfur dioxide when coal is burned (Beer et al., 1992). 

There are six mineral systems Isometric, Hexagonal, Tetragonal, Orthorhombic, Monoclinic, and Triclinic. The Trigonal... 

The possible presence of isotropic materials, including fiberglass, diatomaceous earth, perlite or any isometric mineral has been eliminated. The substance is anisotropic. The following possibilities exist ... 

Ruthenium Sesquisulphide, RuaSs, occurs in the platinum washings of Borneo and Oregon as the rare mineral lauriie, usually in the form of minute octahedra hardness 7-5, density 6-99. It has a bright metallic lustre and contains a little osmium. Deville and Debray 5 prepared a similar sulphide artificially in the form of isometric crystals, octahedra, and cubes by heating ruthenium with pyrites and borax. 

Fibers axe particles with great length in one dimension compared to much smaller lengths in the other two dimensions. Examples are prisms, needles, and threads or mineral fibers such as asbestos. Recent concern over the health hazard posed by inhalation of asbestos fibers has prompted study of fiber properties in air. There is still not as much known about fibers as isometric particles. 

Cyclosporine is a macrolide antibiotic and has been used as an immunosuppressive agent. Cyclosporine can cause both renal and nonrenal toxicity. Clinically renal toxicity consists of four discrete syndromes which include acute reversible renal functional impairment, delayed renal allograft function, acute vasculopathy, and chronic nephropathy with interstitial fibrosis. Proximal tubular epithelium is uniquely sensitive to the toxic effect. The toxic effect is characterized by isometric cytoplasmic vacuolations (several small equally sized vacuoles in cytoplasm), necrosis with or without subsequent mineralization, inclusion bodies (giant mitochondria), and giant lysosomes. Acute vasculopathy consists of vacuolization of the arteriolar smooth muscles and endothelial cells leading to necrosis. In some cases, thrombotic microangiopathy develops, characterized by thrombosis of the renal micro vasculature. Long-term treatment with cyclosporine results in chronic nephropathy with interstitial fibrosis (Chamey et al., 2004). 

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