Sanidine

K2SO-2 MgSO, and halite and (5) kainite ore, kainite [1318-72-5] 4(KC1 MgSO -11H20, and halite. More than 90% of the estimated potassium reserves occur principally as sylvinite and camaUitite (107). Sylvite, the richest of the minerals at 63% K2O, is the principal economically exploitable reserve. In addition, there are four principal insoluble potassium sUicate minerals, glauconite, leucite, nepheline, and orthoclase—sanidine which range in K2O content from 7 to 22%. These minerals are plentihil but for economic reasons may never be exploited for potassium. 

Fig. 2.39. Na /K+ atomic ratios of well discharges plotted at measured downhole temperatures. Curve A is the least squares fit of the data points above 80°C. Curve B is another emperical curve (from Truesdell, 1976). Curves C and D show the approximate locations of the low albite-microcline and high albite-sanidine lines derived from thermodynamic data (from Fournier, 1981). Small solid subaerial geothermal water Solid square Okinawa Jade Open square South Mariana Through Solid circle East Pacific Rise 11°N Open circle Mid Atlantic Ridge, TAG.

Volfinger, M. (1975) Effet de la temperature sur les distributions Na, Rb et Cs entre la sanidine, la muscovite, la phlogopite et une solution hydrothermale sous une pression de 1 kbar. Geochim. Cosmochim. Acta, 40, 267-282. 

As Sr is highly compatible in alkali feldspar under all conditions, it is likely that so too is Pb, whatever the validity of the Sr-Pb proxy relationship. Leeman (1979) determines Z)pb of 0.84-1.37 for separated sanidine phenocrysts (Or- so) from various acid volcanic rocks, in broad agreement with Equation (37). 

Leeman WP (1979) Partitioning of Pb between volcanic glass and coexisting sanidine and plagioclase feldspars. Geochim Cosmochim Acta 43 171-175... 

Leeman WP, Phelps DW (1981) Partitioning of rare earths and other trace elements between sanidine and coexisting volcanic glass. J Geophys Res 86 10193-10199 Linnen RL, Keppler H (2002) Melt composition control of Zr/Hf fractionation in magmatic processes. Geochim Comsochim Acta 66 3293-3301... 

ABSTRACT The aim of this study was to test portable infrared spectroscopy for non-destructive analysis of ancient construction mortar. Mortar samples from the House of the Vestals, in Pompeii, Italy, were initially examined with traditional analytical techniques, including X-ray fluorescence, X-ray diffraction and thin section analysis. These techniques were used to establish mineralogical and chemical profiles of the samples and to verify the results of experimental field methods. Results showed the lime-based binder was composed of calcite, and the volcanic sand aggregate contained clinopyroxene, plagioclase, sanidine and olivine crystals. 

Anomalously high extended defect concentrations may be achieved in crystals by submitting them to directional stress. For example, Willaime and Gaudais (1977) induced dislocation densities of 10 cm in sanidine crystals (KAlSi30g triclinic), and Ardell et al. (1973) reached a dislocation density of 10 cm in quartz with the same method. 

Table 5.62 Chemical analyses of some natural feldspars (Deer et al., 1983). (1) orthoclase (Mogok, Burma) (2) Adularia (St. Gottard, Switzerland) (3) anorthoclase inclusion in augite (Euganean Hills NE Italy) (4) sanidine from a nepheline-leucitite (5) albite from a pegmatite (6) anorthite from a calc-silicatic rock. ...

Helgeson et al. (1978) have shown that the enthalpy of disordering in sanidine is similar to that observed in albite—i.e.. 

Figure 5.58 Phase stability relations in (pseudo) binary system NaAlSi308-KAlSi308 at various P and T conditions (Le = leucite Or = orthoclase Sa = sanidine L = liquid V = vapor). Here, orthoclase identifies simply an intermediate state of substitutional disorder.

Figure 5,59 Effects of structural and coherence state on extent of unmixing in the NaAl-Si308-KAlSi30g binary join. (A) Maximum microcline-low albite, based on data from Bachinski and Muller (1971) and Yund (1974). (B) Sanidine-high albite, based on data from Thompson and Waldbaum (1969) and Sipling and Yund (1976).

The Albite-Anorthite (Roozeboom Type I) and Albite-Sanidine (Roozeboom Type II) Systems as Examples... 

The system is strictly binary only for T < 1078 °C. In K-rich compositions at higher T, the sanidine solid mixture (Sa jn.) is metastable with respect to the leucite solid mixture (K, Na)AlSi206 (Le jn.)- On the Na-rich side of the join (Abg jn.) the crystallization trend of an initial liquid mixture of composition Cl (80% Ab by weight) is similar to that of the previous example. On the K-rich side of the join, cooling of an initial composition C2 (50% Ab by weight) leads to initial formation of crystals the residual liquid moves along the liquidus curve until it reaches the peritectic reaction point P (T = 1078 °C). At P, Le jn. converts into while T remains constant. As shown in figure 7.6B, the... 

Figure 7,6 Phase stability relations in pseudobinary system NaAlSi30g-KAlSi30g, after Waldbaum and Thompson (1969). (A) High-T relations loop of metastable persistency of sanidine like a Roozeboom type III. (B) Expanded T-range with decreasing T, a solvus held opens downward.

Figure 10.4 shows normalized Ba/K and Sr/K distributions between sanidine and a hydrothermal solution (liyama, 1972), Li/K between muscovite and a hydrothermal solution (Voltinger, 1970), and Rb/Na between nepheline and a hydrothermal solution (Roux, 1971b), interpreted through the local lattice distortion model, by an appropriate choice of the Nernst s law mass distribution constant K and the lattice distortion propagation factor r. 

Table 10.2 Upper concentration limits for Henry s law behavior in silicates and oxides. Abbreviations Ab = albite Sa = sanidine PI = plagioclase Pel = alkaline feldspar Rb-fel = Rb-feldspar Ne = nepheline Mu = muscovite 01 = olivine Di = diopside Cpx = clinopyroxene Oxp = orthyporoxene Amph = amphibole Par = pargasite Gr = garnet Ilm = ilmenite ...

Blasi A., Brajkovic A., and De Pol Blasi (1983). Dry-heating conversions of low microcline to high sanidine via a one-step disordering process. Abstr. NATO Advanced Study Inst, on Feldspars and Feldspatoids, Rennes, France. 

Brown B. E. and Bailey S. W. (1964). The structure of maximum microcline and the sanidine-microcline series. Norsk Geol Tidsskr,... 

Eugster H. P. (1954). Distribution of cesium between sanidine and a hydrous fluid. Carnegie Inst. Wash. Yb., 53 102-104. 

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