Most diamonds found in the earth are not perfect – they have yellow and brownish tints or they have visible internal flaws that make a s...
Most diamonds found in the earth are not perfect – they have yellow and brownish tints or they have visible internal flaws that make a stone look unclean. These problems, however, can be treated using a variety of enhancement methods.
Color Enhancing Treatments – HPHT
HPHT involves the application of extremely high pressures and temperatures to a rough or polished diamond, resulting in a change of colour. HPHT treatment can transform brown type II diamonds to near colourless or colourless, and rarely can result in pink or blue diamonds from type II stones. Type I brownish coloured stones can be transformed to fancy yellow or fancy greenish yellow.
Color Enhancing Treatments – Irradiation
Irradiation of diamonds involves the use of high energy particles to change the crystal lattice of a diamond. The alteration in the crystal lattice results in a change of colour in the diamond.
The colours produced by irradiation vary due to the colour of the starting material and the method of irradiation used.
After irradiation, diamonds can also be heated under special conditions (called annealing) to further change their colour to a number of attractive fancy colours.
Clarity Treatments- Laser Drilled Diamonds
Laser drilling is used to make the appearance of dark coloured inclusions less obvious. A laser drills into the diamond and intense heat vapourize the inclusion, or an acid is used under special conditions to etch away the inclusion. The treatment leaves a very fine drill hole, and where acid is used, the results are a white inclusion which is the same shape and size as before but without the dark colour of the original inclusion.
Laser drilling is a stable treatment which won't change over time or if subjected to heat, but should be disclosed at the point of sale.
Laser drilling can be picked up by the use of the hand lens or microscope, where the drill hole and the laser channel can be detected.
Clarity Treatments - Fracture Filled Diamonds
Fracture filling involves the use of a high refractive index glass, which is used to fill surface reaching fractures so as to minimise the appearance of the fracture. Fracture filling can be identified using the microscope by the "flash effect" of dispersed colours seen under dark field lighting.
Fracture filling is not a stable treatment and MUST be disclosed at the point of sale. The glass filling is susceptible to heat and can perspire out of a fracture or sometimes change colour if the diamond is heated when jewellery is repaired. For this reason, stones that have been fracture filled cannot be issued a colour or clarity grade because the appearance of the stone changes dramatically when the diamond is first treated and the changes in the diamond are not permanent.
