It is important to perform the determination of the gold/quartz ratio in a gravity concentrate or very rich material. In order to do this the prospector must use the specific gravity of and quartz lightly lower than the maximum values due to the presence of impurities have influence. In this, consider the specific gravity of gold = 19.000 and the specific gravity of quartz = 2.600. These numbers can be corrected when experiment shows the specific gravities to be different. For example, the specific gravity of a mixture of gold and quartz is 8.067. Then, deduct the specific gravity of the mixture from the specific gravity of the gold: the difference is the ratio of the quartz by volume: 19.000-8.067 = 10.933.
Now, deduct the specific gravity of the quartz from the specific gravity of the mixture: the difference is the ratio of the gold by volume: 8.067 - 2.600 = 5.467. Add these ratios together, and proceed by the rule of proportion. The product is the percentage of gold by bulk: 10.933 + 5.467 = 16.400 16.4 is to 5.467 as 100 is to 33.35. Multiply the percentage of gold by bulk, by its specific gravity. The product is the ratio of gold in the mixture by weight: 33.35x19.00 = 633.65. Multiply the percentage of quartz by bulk, by its specific gravity. The product is the ratio of the quartz in the mixture by weight: 66.65x2.60 = 173.29. in order to find the percentage of gold, add these ratios together, and proceed by the rule of proportion: 633.65 + 173.29 = 806.94; 806.94 is to 633.65 as 100 is to 78.53 Hence, a mixture of quartz and gold, having the specific gravity of 8.067, contains 78.53 per cent, of gold by weight.