Labradorite fines

FTIR Spectra. After reaction, the mineral samples were subjected to ultrasonic treatment in acetone for periods of up to 1 hour. Transmission IR spectra of the released product fines from reactions of 60-mesh labradorite and microcline with 10 2 mol dm 3 CsCl in distilled water at 150 C for 47 days are presented in Figure 3. The spectrum obtained from of the labradorite reaction product (Figure 3(a)) is identical with that of a sample of natural pollucite (Figure 3(c)). The spectrum obtained from the microcline reaction product (Figure 3(b)) contains bands in the 500 cm""1 to 800 cm"1 region, due to unreacted microcline, in addition to the major bands of pollucite. Heating the samples overnight at 105 C resulted in the disappearance of the water absorption bands at about 3500 cm 1 and 1680 cm 1. 

Figure 3. FTIR spectra of (a) fines removed ultrasonically from 60-mesh labradorite (see text) (b) fines removed ultrasonically from 60-mesh microcline (see text) (c) natural pollucite.

Thus, experimental studies relating dissolution rates to defect concentrations are needed. This has been done recently in two different types of experiments where the importance of line defects has been measured. Casey et al. (1988) and Holdren et al. (1988) have measured the rate of dissolution of rutile and labradorite powders that were shocked with an explosive charge to induce a high density of dislocations (> 1011 cm-2). Concurrently, in order to avoid artifacts due to fine particles, Schott et al. (1989) have performed with the rotating disc apparatus dissolution runs of single crystals of calcite in which dislocations were induced in a constant-strain apparatus. Examples of the results are shown in Fig. 15. Surprisingly, it can be seen that dislocations have only a small effect on the dissolution rates the dissolution rates of samples with over 6 order of magnitude in dislocation density differ only by a factor less than 3. 

Initial mineral grains were ground in a jaw crusher. The plagioclase and the apatite are sieved at 0.5-1 and 1-2 mm, respectively. The 0.5-1 mm fraction was magnetically sorted in order to remove grains containing ilmenite. Apatite and labradorite grains were also treated ultrasonically and washed with distilled water in order to remove the fine particles. 

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