Properties of feldspar

Table 5.65 Thermodynamic properties of feldspar end-members in various structural forms according to Helgeson et al. (1978). Heat capacity function Cp= K + K Y +...

Smith I V. (1983). Some chemical properties of feldspars. In Reviews in Mineralogy, vol. 2 (2d ed.), P. H. Ribbe (series ed.), Mineralogical Society of America. 

Gandais, M., Willaime, C. (1984). Mechanical properties of feldspars. In Feldspars and Felspathoids Structures, Properties and Occurrences, edited by W. L. Brown, pp. 207-46. NATO ASI Series. Dordrecht D. Reidel. 

Among the properties of feldspars, mention should be made in particular of their behaviour around the melting point. The polymorphic transformations are of less significance because alkali feldspars usually turn into melt and into glass after cooling. 

Alumina in combination with siUca is present in limestone chiefly as clay, though other aluminum siUcates in the form of feldspar and mica may be found. When present in appreciable quantities, clay converts a high calcium limestone into a mad or argillaceous stone, which when calcined yields limes with hydrauhc properties. Limestones containing 5—10% clayey matter yield feebly hydrauHc limes those containing 15—30% produce highly hydrauHc limes. 

Sulfide collectors ia geaeral show Htfle affinity for nonsulfide minerals, thus separation of one sulfide from another becomes the main issue. The nonsulfide collectors are in general less selective and this is accentuated by the large similarities in surface properties between the various nonsulfide minerals (42). Some examples of sulfide flotation are copper sulfides flotation from siUceous gangue sequential flotation of sulfides of copper, lead, and zinc from complex and massive sulfide ores and flotation recovery of extremely small (a few ppm) amounts of precious metals. Examples of nonsulfide flotation include separation of sylvite, KCl, from haUte, NaCl, which are two soluble minerals having similar properties selective flocculation—flotation separation of iron oxides from siUca separation of feldspar from siUca, siUcates, and oxides phosphate rock separation from siUca and carbonates and coal flotation. 

Part of this program was realized at the Survey. Between 1901 and 1907, the chemist Allen, the physicist Day, and the petrographer, Iddings, completed a rigorous study of the thermal properties of the plagioclase feldspars, the most abundant rockforming minerals. This study was important in several respects. 

Carpenter M. A. and Ferry I M. (1984). Constraints on the thermodynamic mixing properties of plagioclase feldspars. Contrib. Mineral Petrol, 87 138-148. 

As one might expect there is an approximate correlation between the solid state structure and the physical properties of a particular silicate. For instance, cement contains discrete 8104 units and is soft and crumbly asbestos minerals contain double chains of 8104 units and are characteristically fibrous mica contains infinite layers of 8104 units, the weak bonding between the layers is easily broken, and micas show cleavage parallel to the layers and granite contains feldspars that are based on three-dimensional 8104 frameworks and are very hard. 

The distinctly differentiated results obtained, for example, for different faces of quartz or feldspar crystal, with clear observed differences depending on structure and compactness of the material under test, are an argument for wide use of the Mackensen blower in the study of engineering properties of rocks and ceramic materials and also in hardness estimation of minerals. 

Three Hanford sediments were used in the sorption studies. Each of these sediments contained significant quartz, feldspar, vermiculite, mica, and montmorillonite and were typical of the Hanford sediment in which the HLW tanks are located. Properties of the sediments used are given in Table H. 

During this century there has been considerable interest in the application of thermoluminescence studies to the recent history of meteorites. Natural TL provides a means of exploring radiation history and thermal environment in a manner which is complementary to isotopic methods, and the measurement of natural TL is now routine for the numerous meteorites being returned each year from the Antarctic (3,4). However, induced TL measurements have also proved of considerable interest, because the measurements have implications for the earliest history of meteorites. Essentially, the induced TL properties of meteorites are determined, with a few notable exceptions, by the amount and the nature of the feldspar in them, and feldspar is very sensitive to the major processes experienced by meteorites. In the present paper, we describe our recent work on the induced TL properties of meteorites and briefly discuss how these data relate to early meteorite history. We emphasize the relationship between the TL data and mineral properties. We also present here detailed descriptions of the cathodoluminescence properties of primitive meteorites, as these provide new insights into mineralogical controls on TL properties. 

Laboratory Studies of the Induced Thermoluminescence Properties of Ordinary Chondrites and Feldspar... 

A major study of the TL properties of terrestrial and synthetic feldspars is warranted, but it is clear from existing data that annealing not only affects disordering, but it also affects peak temperatures and that the two are somehow related. 

Aluminosilicates form an extensive family of compounds that include layered compounds (such as clays, talc, and micas), 3-D compounds, (e.g. feldspars, such as granite), and microporous solids known as molecular sieves. The structural diversity of these materials is contributed to by aluminum s ability to occupy both tetrahedral and octahedral holes as it also does in y-Al203. Thus, aluminum substitution for silicon in silicate minerals may lead to replacement of silicon in tetrahedral sites or the aluminum can occupy an octahedral environment external to the silicate lattice. Replacement of Si with Al requires the presence of an additional cation such as H+, Na+, or 0.5 Ca + to balance the charge. These additional cations have a profound effect on the properties of the aluminosilicates. This accounts for the many types of layered and 3-D structures (see Silicon Inorganic Chemistry). 

---