Diamond is the hardest natural substance known, and nothing can mark it. If you can mark it, it's definitely not a diamond.

2. Thermal conductivity test

At the same time, breathe into the diamonds and other similar objects to be debated. If it is a diamond, the water mist condensed on its surface should evaporate faster than other objects, because the thermal conductivity of the diamond is high.

Step 3 Observe the reflected light

With a magnifying glass, it can be observed that the waist of the diamond presents a very fine matte shape, and the reflected light shines. This characteristic of diamonds is unique.

Step 4 look at the growing point

Observing under a magnifying glass, there are often grooves and triangular growth points on the crystal face of real diamonds, while there are three kinds of fakes:

(1) Ordinary glass containing alumina is easy to be misplaced due to the increase of refractive index and dispersion, but its hardness is low.

(2) Imitated with chemically synthesized sapphire and colorless spinel, the hardness is similar, but the refractive index is low and has birefringence, and the double image can be seen under a magnifying glass.