Positively tests for diamonds and simulants. This is one of few testers that allows the user to change sensitivity according to size of the stone being tested. Most diamond testers are factory pre-set to test for "average" size stones. Thus, when testing very small (under 5 point) or large (over 1 carat) stones, you can get false results because the tester is fooled about the size of the stone. With the Diamond Sure I, adjusting the sensitivity eliminates erroneous results. Compact design makes it easy to handle and test for several stones. Will not test for moissanite.