Locked mineral particles

This highly hygroscopic molecule readily combines with water molecules to form an acid aerosol droplet. Other aerosols are formed by nucleation around mineral particles injected as a result of volcanic activity. Under very cold conditions, such as at the poles in winter, these aerosols freeze to form polar stratospheric ice clouds (PSCs), the surfaces of which provide a substrate for important heterogeneous catalytic processes. An example of this is the well-known ozone hole effect. This arises because the steady state concentration of O3 is sustained by the series of reactions (5.1) and (5.21)-(5.25). As already discussed, the sink mechanism (5.24) and (5.25) requires the presence of catalyst X, of which Cl atoms are nowadays the most important, and which are provided, such as reaction (5.26), mainly by the photolysis of CFCs present at trace levels in the upper atmosphere and much of the Cl is temporarily locked up into the reservoir species such as HCl and ClOx-... 

Basic Requirements for Spiral Concentration Minerals or materials of different specific gravity can usually be concentrated on spirals if the heavy particles do not exceed 10 mesh (2 mm) or are not finer than 200 mesh (0.074 mm). The size of the low-specific-gravity component is not critical when the values to be recovered are in the heavier-particle fraction. In this case the size of the light particles may range from 4 mesh (4.76 mm) to zero. The quantity of locked grain components (referred to as middlings in the mineral industry) that are present in a given pulp can be critical because this material is fre-... 

Figure 2. Comparison of SE (left) and BSE images (right) from the same area of pyrite and muscovite (mica) graias showing composites of the two minerals. The central muscovite particles have locked regions of pyrite (light contrast in BSE image) not liberated during grinding of the ore.

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