Appraisal Difference of CVD Synthetic Diamond and Natural Diamond

Synthetic diamonds and their processing cost remain high, especially in the aspects such as equipments, technology and process requirements. Now there are a small amount of synthetic diamonds in the world market, but there is no price advantage. The main appraisal characteristics:

A. Inclusions
With different shape alloy inclusions, these inclusions have many shapes, such as round, rod, plate, needle, etc. Its arrangement mode is associated with internal growth zone boundaries. Inclusions can be dispersed in the crystal in form of particles. These inclusions are not transparent, shown in golden brown or black, with metallic luster.

B. The color
Most of synthetic diamonds are shown in yellow, while natural diamonds are colorless, yellow and other colors.

C. Absorption lines
Synthetic diamonds do not have the colorless and yellow series in natural diamonds, with a 415nm most characteristic spectral lines. And most of natural diamonds are I a model, while synthetic diamonds are mainly Ⅰ b type, double atomic aggregate nitrogen is rare case that exists.

D. Abnormal birefringence
Under orthogonal polarization, the complexity of natural diamond in growth and migration process can show complicated abnormal birefringence characteristics, such as irregular strip, waving,and grid shape, while the abnormal birefringence performance of synthetic diamond is weak, some synthetic diamonds are shown in crossed bright band.

E. Luminescence characteristics
Ultraviolet fluorescence: some synthetic diamonds are inert under long-wave ultraviolet light, and show moderate to strong yellowish green fluorescence under short-wave ultraviolet light, also with zoning phenomenon. Its fluorescence characteristics are different from natural diamonds.
Cathodoluminescence instrument (under the electronic excitation) :
Synthetic diamond: The colors(yellow, yellow-green); rules partition (the main body, octahedral area)
Natural diamond: The blue is given priority, with layered growth or complex form

F. Crystal shape and surface characteristics
Synthetic diamonds have octahedral and cubic shapes as the main body, and can develop the dodecahedron, the four split face body or triangle split surface crystal face.
The surface may show the dendritic growth lines or irregular hills, which is different from natural diamonds.