Find a normal sized drinking glass and fill it ¾ of the way with water. Carefully drop the loose stone into the glass.
If the gemstone sinks, it’s a real diamond. If it floats underneath or at the surface of the water, you have a fake on your hands.
A real diamond has high density, so the water test shows if your stone matches this level of density.
For the fog test, hold the diamond or ring between two fingers and breath on it with a puff of air. A light fog will form on the diamond because of the moisture and heat in your breath.
If the fog dissipates right away, the diamond is real. If it takes several seconds for the fog to disperse, it is likely a fake diamond.
Diamonds effectively conduct heat and therefore disperse heat quickly.
The Dot Test
If you don’t have newspaper to use, the dot test is an excellent alternative.
Place a white piece of paper on a flat surface and draw a small dot with a pen. Lay the stone onto the dot with the flat side down. Through the pointed end of the diamond, look down onto the paper. If you see a circular reflection inside the gemstone, the stone is fake. If you cannot see the dot or a reflection in the stone, then the diamond is real.
Because a true diamond has powerful refractive qualities, light will bounce in different directions instead of a straight line. This is why you won’t be able to see letters or dots through a natural, real diamond.