| http://www.w3.org/ns/prov#value | - In some embodiments with the median particle size at least about 7 microns, an additional abrasive may be used, selected from the group consisting of pumice, perlite, precipitated silica, calcium carbonate, rice hull silica, silica gels, aluminas, phosphates including orthophosphates, polymetaphosphates, pyrophosphates, other inorganic particulates, and mixtures thereof.
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