Many clients have been asking certain similar questions about CVD diamond color enhancement (HPHT treatment/ annealing). I have concluded as below:
1) What kind of CVD diamond could be treated? -IIa type with Nitrogen inside. Both roughs and semi-polished could be treated directly. It is not suggested using loose diamond. As after HPHT treatment, there is very thin treatment surface, it has to be polished. Thus, the best way to keep the largest diamond weight is using semi-polished stones or roughs.
2) Could natural diamond do annealing? -Natural diamond also could do, but should be IIa diamond. For natural diamond, it requires higher pressure and higher temperature, compared with CVD one. If it's other type, like Ia type, after HPHT treatment, it may turn into different colors, pink, green, yellow etc. We have done experiments and taken photos after treatment. (see below photos)
3) How long takes to do CVD diamond color enhancement?-To put diamond into pyrophyllite cube, then for whole process, it takes within 30mins, which means within 30mins, results could be witnessed. Thus, in our factory, we always provide quick feedback. Generally, after receiving customers' stones, we shall return within 1-2 days.
4) How many carats diamonds could we treat?- Now each month our treatment capacity is over 20,000cts.
5) Would CVD diamond be burnt or broken?-If there is no crack or defect on CVD diamond surface, we could fully control diamond without broken during HPHT process. In our factory, we have been using special technology to control temperature. So burnt is impossible here. If roughs used directly for annealing, polycrystalline must be completely removed, which would cause broken.