A sample of marble chips from Carrara, Italy was found to have the particle size analysis shown in Table IV below:8 Kg of the marble chips were mixed with water containing 0.3% by weight of calcium hydroxide based on the weight of dry marble chips,Small Scale Gold Mining Equipment, the solids content of the aqueous slurry being 40% by weight. The aqueous slurry was ground in a peble mill with flint pebbles having diameters in the range from 25 to 38 mm and it was found that after grinding for 2 hours the particle size distribution of the ground marble was such that only 0.83% by weight of the particles had a diameter greater than 53 microns. The rate of production of marble ground to this fineness was 4 Kg per hour.
A second sample of marble chips from the same source had the particle size analysis shown in Table V below:Kg of the marble chips were mixed with water containing 0.3% by weight of the sodium polyacrylate dispersing agent described in Example 1, based on the weight of dry marble chips, the solids content of the aqueous slurry being 71.4% by weight. The aqueous slurry was ground in the same pebble mill and with the same pebbles as described above and it was found that after grinding for 5 hours the particle size distribution was approximately the same as that achieved with the first batch as described above. The rate of production of marble ground to this degree of fineness was 4.54 Kg per hour and although this rate of production was slightly higher than that achieved with the first sample the starting material in the case of the first sample was very much coarser and the grinding efficiency is therefore seen to be superior in the case of the first sample.
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