Knowledge is Power!
One stone that caused debate for a long time on an internet forum for scientist, was an unknown stone bought as 'black diamond'. It was not possible get a usual examination under a microscope because of opaque. The store surface was 'pitted' like granite; the specific gravity was not quite correct, and although it certainly registered 'diamond' on a V2 diamond tester, the results on a Moissanite tester were unsure, it depended on where the probe was placed on the stone.
Actually it was not diamond, it was Moissanite. Even without scientist spending a few hours examining and testing the stone, there were two alarming. Firstly, it was bought in Afghanistan, and most stones sold in this area are not real. Secondly, the proof that it was natural black diamond came in the form of a lab report from New Delhi, from "an ISO 9001:2008 Company comprising GIA alumni." A certificate is worthless unless you can check that the company is real - and even then, you need the skill to match the stone with the certificate. Do you believe sellers when you buy a diamond? The above story is a warning to everyone. You are not sure that you buy a valuable stone after a very long time haggling they agreed a price. Moreover, most of us are not diamond professionals that can tell what it is. Although not all stones can be tested by diamond tester tools, it at least could give a hand for most stones. A small device might avoid a big case of victimization without any awareness.
It is easy to use if you are newer in the area of diamond. You may even know the Diamond accurately with the help of LED Diamond Tester tool rather than a professional. Before going into a diamond store, have tester tool prepared prevent getting ripped off in illegal business.