A diamond is a naturally crystallized form of carbon valued as a precious gem. Due to the high cost of diamonds, artificial gems are sold as a less expensive alternative. A rhinestone, for instance, is a diamond simulate typically made from crystal or glass. Before you buy a piece of jewelry, learn the difference between a real diamond and a fake.
Hold the rhinestone between your index finger and thumb with the point facing down. Run the rhinestone over a piece of glass using very little pressure. Do the same with the diamond. A rhinestone may slightly scratch the glass, whereas a diamond will create a definite cut on the glass.
Place the rhinestone and diamond upside-down on a piece of newspaper. Try to read the newsprint through the stone. You will be able to see the words through the rhinestone but not through the diamond.
Hold the rhinestone in front of your mouth and breathe on it as you would to fog a mirror. Look at the stone. Do the same for the diamond. The diamond will display no moisture on the surface while the rhinestone will stay fogged for several seconds.
Hold both stones under a black light. The stone that fluoresces with a blue color is the diamond.
Place a small drop of water on the face of the rhinestone and the diamond. Move the stones in a circular motion. The water will disperse on the rhinestone face, whereas the drop will stay in a perfect globular form on the diamond.
Drop the rhinestone into a clear glass of water. In another glass, drop the diamond. The diamond should be visible in the glass of water while the rhinestone will be nearly invisible.
Compare the price of the diamond and rhinestone, if you're purchasing from a retailer. If the items are similar in size but one is significantly less expensive, the cheaper of the two will be the rhinestone.
Take both the rhinestone and the diamond to an appraiser at a local jewelry store. Ask him to look at the stones. Pay any fees and wait for the results. This method of comparing rhinestones and diamonds is the most accurate.