The word diamond is derived from the ancient Greek ada-mas - invincible. Diamond is the hardest known natural material. It reaches the highest degree of hardness, 10, on the Mohs scale of hardness. The group of corundum minerals (e.g. ruby, sapphire) reaches a hardness degree 9. Although there is a difference in just one level, a diamond is 140 times harder than corundum. This difference is the same as between degree 1 and 9.

Diamonds have a specific mass of 3,51g/cm3. Thanks to this property diamonds settled in river beds and created so called alluvial deposits. The specific mass is therefore the basic indicator in determining the authenticity of diamonds.

Diamonds possess 6 times higher thermal conductivity than copper. This property is used for both testing diamonds and their application in nanotechnologies.

This property of diamonds was first utilized in the 60s of the 20th century for grading of diamonds. Every diamond exposed to X-rays radiates and can thus be separated from other rocks. The fluorescence of diamonds is usually blue but can also be white, violet, yellow, green or orange.

According to transparency we distinguish diamonds from absolutely clear to completely opaque. Only the best stones are set in jewellery. Other stones are used in industry where they play an indispensible role.

The refractive index in diamonds reaches a specific value of 2,417 and lends the diamond its unique optical phenomena, which also serves for determining its authenticity.

The number of reflections, when moving a cut stone or the source of light, is called sparkling brilliance. The number of light reflections depends on the number of facets and on their proper size.

The white colour around us is actually composed of a whole scale of colours from red to violet. Depending on what range of colour is absorbed or radiated, creates the resulting colour. Almost all diamonds contain atoms of other elements. Atoms of nitrogen are most common and they cause a yellow colouring that we can see (e.g. it absorbs the blue spectrum). Boron causes a blue colouring (absorbs the yellow spectrum). Other colour alternations are caused by different mechanisms, for instance by deformation of the crystalline lattice – pink diamonds, or radiation – green diamonds etc. Diamonds without any other element are completely colourless.