The GIA reports that rapid progress in the last few years in High-Pressure, High-Temperature (HPHT) technology is now being used to produce melee-size diamonds around 2–3 mm in diameter and large colorless single crystals all with significantly improved quality and growth rate. A Russian company is reportedly growing multiple large, gem-quality colorless diamond crystals in a single run, while the GIA reports on large diamond crystals manufactured using a similar technology by Jinan Zhongwu New Materials Co. Ltd in Shandong, China.
GIA officials visited the Chinese factory in early March and obtained 50 crystals which were examined using the instrumentation and techniques applied to all diamonds submitted to GIA for grading. Weighing from around 0.5 carat to 1.2 carats, they all exhibited typical characteristics of HPHT growth and were identified as synthetic. They were basically colorless, with only a few metallic inclusions observed. According to the manufacturer, large quantities of gem-quality colorless and blue diamonds are produced in the factory, in sizes up to 3.5 carats. "While the total production volume remains unclear, it is undoubtedly significant, and capacity is likely to expand in the near future. This strongly suggests that even more large HPHT synthetic diamonds will be introduced into the jewelry industry."