text: what is the best way to tell if a gem is fake? i have a few gemstones i won in an auction. what is the best way to determine if they are real or not? i do not want to take them to a jewelers just yet, cause that will probably cost money to get them looked at.... wieght vs volume find out what the stones should weigh per unit of volume. measure their volume by dropping them in a graduated cylinder and recording the water level before you drop it in and after. the difference is your volume. wiegh the stone and see how closley it resembles the wieght it should.  not going to be exact, because of natural flaws in stone making them a bit off with the weight, but it will give you a guess of whether they could be real or not.