Crystalline minerals

Corundum. Comndum [1302-75-5] (see Aluminum compounds) is a naturally occurring massive crystalline mineral composed of aluminum oxide. It is an impure form of the gems mby and sapphke. Prior to 1900 comndum was an important abrasive for the production of grinding wheels. Today it is mainly employed as a loose abrasive for grinding and polishing optical lenses. Almost all the world s supply of comndum now comes from Africa, primarily from Zimbabwe. 

Hydrothermal crystallisation processes occur widely in nature and are responsible for the formation of many crystalline minerals. The most widely used commercial appHcation of hydrothermal crystallization is for the production of synthetic quartz (see Silica, synthetic quartz crystals). Piezoelectric quartz crystals weighing up to several pounds can be produced for use in electronic equipment. Hydrothermal crystallization takes place in near- or supercritical water solutions (see Supercritical fluids). Near and above the critical point of water, the viscosity (300-1400 mPa s(=cP) at 374°C) decreases significantly, allowing for relatively rapid diffusion and growth processes to occur. 

The crystalline mineral silicates have been well characterized and their diversity of stmcture thoroughly presented (2). The stmctures of siHcate glasses and solutions can be investigated through potentiometric and dye adsorption studies, chemical derivatization and gas chromatography, and laser Raman, infrared (ftir), and Si Fourier transform nuclear magnetic resonance ( Si ft-nmr) spectroscopy. References 3—6 contain reviews of the general chemical and physical properties of siHcate materials. 

Gopper(II) Sulfates. Copper(II) sulfate pentahydrate [7758-99-8] CuS04-5H20, occurs in nature as the blue triclinic crystalline mineral chalcanthite [13817-21 -5]. It is the most common commercial compound of copper. The pentahydrate slowly effloresces in low humidity or above 30.6°C. Above 88°C dehydration occurs rapidly. 

Secondary minerals. As weathering of primary minerals proceeds, ions are released into solution, and new minerals are formed. These new minerals, called secondary minerals, include layer silicate clay minerals, carbonates, phosphates, sulfates and sulfides, different hydroxides and oxyhydroxides of Al, Fe, Mn, Ti, and Si, and non-crystalline minerals such as allophane and imogolite. Secondary minerals, such as the clay minerals, may have a specific surface area in the range of 20-800 m /g and up to 1000 m /g in the case of imogolite (Wada, 1985). Surface area is very important because most chemical reactions in soil are surface reactions occurring at the interface of solids and the soil solution. Layer-silicate clays, oxides, and carbonates are the most widespread secondary minerals. 

Oxides, non-crystalline minerals, and humified organic matter can also develop charges at their surfaces by reactions with the soil solution. In this case, the surface can have positive (CEC)... 

Inorganic fillers in plastics compositions are usually in a very finely divided form and, as such, are ideal for powder XRD study. A sample size of a few mg gives a good pattern in 1 or 2 h. Crystalline mineral fillers can usually be observed directly in the complete polymeric formulation, in concentrations exceeding about 1 %. Combined XRD/XRF studies are favoured [326]. A mineral filler is easy to identify in a compound in the absence of other fillers. 

The silicates are a large class of solids of great importance in industry as well as science, particularly geology. The prototype silicate is quartz consisting of Si04 tetrahedra which share their comers and edges and are arrayed in various three-dimensional patterns depending on the temperature. In other crystalline minerals the tetrahedra are linked in one-dimensional chains, or two-dimensional sheets. The arrays in these latter cases are combined with various metal ions. 

Fig. 3. Soil inventory of carbon in soil organic matter (SOM) (a), A14C of SOM (b), noncrystalline minerals (c), and crystalline minerals (d) versus age of soil substrate. Filled circles, total profiles filled triangle, surface (O and A) horizons (Tom et al. 1997).

With time, schwertmannite progressed to a more crystalline mineral (low crystalline goethite), even under unfavourable kinetic conditions (T<4°C) ... 

A division based on crystallinity facilitates our discussions of both mineral and synthetic fibers by accentuating the morphology of the fibrous object rather than its source or composition. Further, although both amorphous and crystalline mineral fibers are known, most of these used in commerce—and certainly the best known—are crystalline. The opposite is true for synthetic or man-made inorganic fibers (MMIF). The fibers used in commerce are predominantly amorphous. 

FeOOH (synthetic) and its poorly crystalline mineral form, feroxyhyte (5 -FeOOH), are reddish-brown, ferrimagnetic compounds. Their structures are based on hep anion arrays and differ in the ordering of the cations. Feroxyhyte was first described by Chukhrov et al. in 1976 and occurs (rarely) in various surface environments. 

Microwave solidification is an ex situ mixed-waste treatment process. The process is applicable for homogeneous, wet or dry, inorganic solids. The process dries the waste, mixes it with a matrix modifier, transfers it to a processing container, and subjects the mixture to microwave energy to melt the materials. The processed waste form then cools and solidifies to form crystalline mineral analogs. 

XRD was used to identify crystalline mineral phases in the samples. A Rigaku-Geigerflex goniometer was used (copper X-ray source, 45 kV, 35 mA, 1575 W). Samples were run in triplicate and a fourth run was conducted after tungsten was added to one of the replicates as an external standard. The data were evaluated for possible crystalline phases using the PC-based search and match program MICRO-ID (Materials Data Corp., Livermore, CA). 

The sum of these observations suggests that metal phosphate crystalline mineral phases, some of which are solid solutions, are present in the samples. These phases may be discrete or surface precipitates. Some work on scmbber residues using depth profiling techniques with secondary ion mass spectrometry (SIMS) suggest that surface... 

If a species sorbs to a crystalline mineral surface, in an ideal case, no more sorption occurs when all the available surface sites are occupied and concentrations in the solid phase remain constant ( ). In reality surface precipitation may occur, resulting in a sorption isotherm schematically shown in Fig. 4 ( ). 

The acoustic micrograph in Fig. 1.5(a) came from a 5-week-old preparation. It was fixed in alcohol, and stained for alkaline phosphatase and, with von Kossa stain, for biomineral material. The biomineral material of interest here is hydroxyapatite, the principal crystalline mineral constituent of bone. The ordered structure visible within the matrix is not seen with either the light or electron microscopes. But the acoustic microscope can also work perfectly well with unfixed, unstained specimens. Figure 1.5(b) is an acoustic micrograph of matrix and cells from a 17-year-old male. In addition to the standard ingredients of culture medium, these cells were specifically stimulated with beta-glycerolphosphate and a vitamin C preparation. Because the acoustic... 

Chondrules exhibit a bewildering variety of compositions and textures (F ig. 6.1 a,b). Most are composed primarily of olivine and/or pyroxene, commonly with some glass. (For a crash course in mineral names and compositions, see Box 6.1.) If melt solidifies so quickly that its atoms cannot organize into crystalline minerals, it quenches into glass. Iron-nickel metal and iron sulfide occur in many chondrules, often clustered near the peripheries. The textures of... 

Mineralogical interpretations of Halley dust analyses remain controversial. Lawler et al. (1989) saw no clustering of compositions that might suggest crystalline minerals (Fig. 12.5), whereas Fomenkova et al. (1992) identified compositions that were consistent with a number of minerals, including pyroxene, phyllosilicate, carbonate, FeNi metal, iron sulfide, and iron oxide. The characterization of minerals in returned comet dust (see below) supports the identification of some of these primary minerals but calls into question the identification of those formed by alteration. 

The current synthesis of ethyl alcohol eliminates sulfuric acid and uses phosphoric acid suspended on zeolite substrates. Zeohtes are porous aluminosilicate crystalline minerals. The use of phosphoric acid as a catalyst allows the direct hydrolysis of ethylene into ethyl alcohol C2H4 + H20 —> C2H5OH. Industrial alcohol is rendered inconsumable by adding a small amount of a poisonous substance such as methanol or acetone to it. Alcohol unfit for consumption because of a poisonous additive is termed denatured alcohol. 

Termine, J. D., Posner, A. S. Infrared analysis of rat bone Age dependency of amorphous and crystalline mineral fractions. Science 153, 1523 (1966)... 

The union of mercury and sulfur is effected in the most simple way of all by merely rubbing the two substances together. The product is a black, amorphous compound, quite unlike the bright scarlet crystalline mineral cinnabar. To convert it into the crystalline form, advantage is taken of the following principle An amorphous form is more unstable than a crystalline form and tends to go over into it. The unstable amorphous form is also more soluble in solvents than the stable crystalline form. If, therefore, a solvent can be found in which both are slightly soluble, the amorphous form dissolves to saturation, but this produces a solution oversaturated with respect to the stable form, and some of this crystallizes out. More of the unstable... 

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