• The hardest mineral (hardness 10). Hardness anysotropy (hardness depends on direction). The high hardness provides for the excellent polish of surfaces and sharp edges, which are persistent in time.
• Diamond has a cubic syngony and, therefore, optically isotropic. However, anomalous double refraction occasionally occurs.
• Perfect cleavage on (111).
• Some kinds of mineral inclusions are typical of diamond.
• Wettability by oils. Unlike imitations, diamond is wetted by oils well.
• Diamond is characterized by a high refractive index (2.42), but has a relatively low density (3.52); most of imitations are heavier.
• Diamond is characterized by a high heat conductivity. Diamond detectors employ this property.
• Diamond is transparent in X-rays and shows a slight blue glow.
• Luminescence of various intensity and color in UV-rays.
• High light reflection (more than 0.17)
• High dispersion (0.044)
• Round brilliant cut provides the characteristic total internal reflection.

   Methods helping to set diamond apart from imitations

• Method of point (for Full Cut and determined proportions). This method is based on the total internal reflection of diamond. A diamond is put its table down on a point drawn on a sheet of paper and examined through the pavilion. If the point is not seen, the tested stone is diamond. Exceptions: strontium titanate and rutile. This method is not universal, since some cutting styles and angles do not provide the total internal reflection.
• Specific weight. A stone is weighted, and then its weight is determined through the formula. If the actual and estimated values are equal (within 10%), it is diamond; if the difference exceeds 10%, it is imitation.
• Heat conductivity. This parameter is measured with a Diamond-detector). Exception: moissanite.
• Reflective ability. Some detectors are based on this property. The intensity of the reflected light is measured in percentage of the intensity of the initial light striking the table of the stone at the right angle.
• Luminescence (indirect method). Mounted diamonds usually have different intensity and color of luminescence in long-wave ultraviolet rays. Imitations are similar in luminescence or show no luminescence at all.
• Hardness. Diamond is the hardest mineral and scratches all imitations.
• Inclusions. Diamond can be identified from typical inclusions. Inclusions also enable an expert to distinguish between synthetic diamonds and imitations.
• Surface examination. Diamond always has smooth facets and sharp edges and facet-junction points, which do not wear down with time.
• Dispersion. Stones with different dispersion show different fire.
• Optical isotropy. Many imitations are anisotropic.
• Characteristic anomalous double refraction.
• Refractive index. All imitations can be recognized by the measurement of the refractive index. However, natural diamond and its synthetic counterpart have the same refractive index.

   Some colorless materials (colorless sapphire, quartz, topaz, beryl, phenakite, spinel, glasses, doublets, etc.) can be recognized with common gemological tools - polariscope, refractometer, spectroscope, etc.

Distinquish of diamond and main imitations.