The basic gold testing procedure is to make a small scratch test of the sample metal you are testing on the Test Stone (#6751). Drop a few drops of the test acid on the sample and observe it. If the quality of the gold/sample metal is equal to or greater then the karat quality rated on the test acid the acid will not effect the sample. If the tested metal is not gold/sample or is of a lower purity then the quality rated on the test acid the test acid will destroy the sample. An optional method is to make two scratches on the stone, one with the sample metal being tested and another with a test needle (#6759) of known purity gold. When you apply the acid you observe both scratches to see how they compare.