Sodium feldspar

In a final application of kinetic reaction modeling, we consider how sodium feldspar (albite, NaAlSisOs) might dissolve into a subsurface fluid at 70 °C. We consider a Na-Ca-Cl fluid initially in equilibrium with kaolinite [Al2Si20s (OF )/ ], quartz, muscovite [KAl3Si30io(OH)2, a proxy for illite], and calcite (CaC03), and in contact with a small amount of albite. Feldspar cannot be in equilibrium with quartz and kaolinite, since the minerals will react to form a mica or a mica-like... 

As a second example, we construct a simple model of how minerals might dissolve and precipitate as rainwater percolates through a soil (Bethke, 1997). The soil, 1 m thick, is composed initially of 50% quartz by volume, 5% potassium feldspar (KSiAEOfO, and 5% albite (sodium feldspar, NaSiAEOx). The remaining 40% of the soil s volume is taken up by soil gas (15% of the bulk) and water (25%). 

Figure 5.55 Mutual dependence of Q i and Q d order parameters. In the upper part of the figure is outlined the T dependence of substitutional disorder Qod for different values of Qdi and, in the lower part, the T dependence of the displacive disorder parameter Qdt for different values of The heavy lines on the surface of local curves represent the solution for thermal equilibrium. From E. Salje and B. Kuscholke, Thermodynamics of sodium feldspar II experimental results and numerical calculations. Physics and Chemistry of Minerals, 12, 99-107, figures 5-8, copyright 1985 by Springer Verlag. Reprinted with the permission of Springer-Verlag GmbH Co. KG.

Natural occurrences in hydrothermal areas show that the replacement of analcite + quartz by albite probably takes place near 150-180°C (Coombs, et al., 1959) at several hundred meters depth. The observed upper limit of analcite appears to be 100-125°C in deeply buried rocks in Japan 5Km depth). In other rocks for which no temperature data are available analcite can be found to coexist with sodium feldspar (High and Picard, 1965 Iijima and Utada, 1966 Iijima and Hay, 1968 Otalora, 196A Callegari and Jobstribitzer, 1964 Gulbrandsen and Cressman, 1960). Several authors have indicated that analcite replaces other zeolites in buried sequences of rocks (Moiola, 1970 Sheppard, 1970 Iijima and Hay, 1968 Iijima, 1970 Gude and Sheppard, 1967) but this is certainly not the rule since analcite is frequently associated with other zeolites as a primary mineral in soils sediments and sedimentary rocks (Hay, 1966). 

Gjonnes, J., Olsen, A. (1974). Study of exsolution structures in sodium feldspars by a combination of electron microscopy and energy dispersive x-ray analysis. In Electron Microscopy 1974, Eighth International Congress on Electron Microscopy, Vol. 1, edited by J. V. Sanders D. J. Goodchild, pp. 504-5. Canberra, Australia Australian Academy of Science. 

The pure members of the feldspar group are (refer to Table 7) sodium feldspar (albite, triclinic) — Na20. AI2O3. 6 SiO ... 

The fusion of both potassium and sodium feldspar starts at about the same temperature however, the potassium feldspar melt has a higher viscosity which is maintained up to higher temperatures, so that the ceramic ware is not as readily deformed as when sodium feldspar is used. For this reason, potassium feldspars are preferred in ceramics, while the glass industry requires sodium feldspars which introduce both Na20 and AI2O3 into the glass batch. 

Feldspars constitute a significant component of igneous rocks and their occurrence in nature is thus very widespread. However, they are not found in pure form potassium feldspar always contains sodium, and sodium feldspar usually contains calcium feldspar. In addition to this, feldspars contain accessory minerals, mainly quartz, mica and other silicates. 

Salje EKH (1985) Thermodynamics of sodium feldspar I order parameter treatment and strain induced coupling effects. Phys ChemMin 12 93-98... 

Salje E, Devarajan V, Bismayer U, Guimaraes DMC (1983) Phase transitions in Pb3(Pi xAS c04)2 Influence of the central peak and flip mode on the Raman scattering of hard modes. J Phys C 16 5233-5243 Salje E, Kuscholke B, Wrack B, Kroll H (1985) Thermodynamics of sodium feldspar 11 Experimental results and numerical calculations. Phys Chem Minerals 12 99-107 Salje E, Wrack B (1983) Specific-heat measurements and critical exponents of the ferroelastic phase transition in Pb3(P04)2 and Pb3(Pi.j,AS c04)2. Phys Rev B28 6510-6518 Schofield PF, Chamock JM, Cressey G, Henderson CMB (1994) An EXAFS study of cation site distortions through the E2/c-ET phase transition in the synthetic cuproscheelite-sanmartinite solid solution. Mineral Mag 58 185-199... 

Demonstration of the zero-order dissolution rate of feldspar and aluminum oxide with respect to the solute concentrations of H4Si04 and Al (III). (A) The increase in the concentration of silicic acid in solution during the dissolution of Amelia Courthouse Albite (sodium feldspar) (Holdren and Berner,... 

The sodium concentration of soils is determined by the geological origin of the rocks. All minerals of the feldspar group (sodium feldspar, potassium feldspar, calcium feldspar), potassium mica and hornblende are rich in sodium. The same applies to the clay minerals montmorillonite and illite. 

Chem. Descrip. Sodium feldspar CAS 1344-00-9 EINECS/ELINCS 215-684-8 Uses Filler, flatting agent for traffic paints, interior/exterior architectural coatings, protective, maintenance and marine coatings, mastics and adhesives... 

Synonyms Aluminosilicic acid, sodium salt Aluminum sodium silicate Silicic acid, aluminum sodium salt Sodium aluminosilicate Sodium aluminum silicate Sodium feldspar Zeolite Zeolites Definition Series of hydrated sodium aluminum silicates produced by reaction of sodium silicate and kaolinite clay Formula NajO AI2O3 SiOa with mole ratio = 1 1 13.2 Properties Wh. fine amorphous powd. or beads, odorless and tasteless insol. in water, alcohol, org. soivs. partly sol. in strong acids and alkali hydroxides 80-100 C pH 6.5-10.5 (20% slurry)... 

The feldspars are subdivided into two groups the alkali feldspars (including mi-crocline, orthoclase, and sanidine), in which potassium is dominant with a smaller proportion of sodium and negligible calcium and the plagioclase feldspars, which vary in composition in a series that ranges from pure sodium feldspar (albite) through to pure calcium feldspar (anorthite) with negligible potassium. Feldspars form colourless, white, or pink crystals with a hardness of 6 on the Mohs scale. 

Sodium etidronate. See Disodium etidronate Sodium feldspar. See Sodium silicoaluminate... 

Synonyms Aluminosilicic acid, sodium salt Aluminum sodium silicate Silicic acid, aluminum sodium salt Sodium aluminosilicate Sodium aluminum silicate Sodium feldspar Zeolite Zeolites Definition Series of hydrated sodium aluminum silicates produced by reaction of sodium silicate and kaolinite clay... 

Most important mineral Albite, sodium feldspar NaAISi Og Halite, rock salt NaCI (Figure M12)... 

Albite (sodium feldspar) NaAlSijOg Triclinic. Plates and rods. A lamellar, leaf-like variety of albite is called cleavelandite A colorless or milky-white mineral... 

The products of the reactions of cryolite components with alumina silica refractories are albite (sodium feldspar) and nepheUne, which may coexist with cryolite. The solubility of alumina and silica in cryolite and sodium fluoride lowers as the acidity of the system decreases, and the freezing point of the system decreases as the silica content increases (from nepheline to albite). 

Natural feldspars used for the preparation of ceramics are mineral mixtures. Thus, the commercial potassium products can contain between 2.5 and 3.5% of albite mass, whereas anorthite and a small quantity of orthoclase, between 0.5 and 3.2%, are often present in the available sodium feldspars [MAN 94]. They can also be incorporated into the paste in the form of feldspathic sand. When these natural products are heated, mixed and homogenous feldspar is formed. This compoimd. 

It is also worth noting that sodium-feldspar is a common authigenic mineral, forming contemporaneously with sedimentation, and that authigenic albite generally shows greater purity than albite from other sources. 

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