- Weight: Similar to natural diamonds, the higher the weight of HPHT rough diamonds, the higher the price. Because larger HPHT rough diamonds are more difficult to cultivate, requiring more precise control of the process and longer cultivation times, a 1 carat HPHT rough diamond, for example, can cost several times as much as a 0.5 carat HPHT rough diamond.
- Clarity: Clarity refers to the presence of flaws and inclusions within the diamond. The higher the clarity, the higher the price of HPHT rough diamonds. Higher clarity HPHT rough diamonds are visually purer and more transparent, e.g. a VVS (Very Very Small Flaw) HPHT rough diamond with almost no internal flaws will cost significantly more than a SI (Small Flaw) rough diamond with visible flaws.
- Color: The closer the HPHT rough diamond is to colorless, the higher the grade and the higher the price. In color grading, grade D (completely colorless) is the highest grade, followed by grade Z (light yellow or light brown). For example, a D-grade HPHT rough diamond will cost much more than an H-grade one, while colored HPHT rough diamonds with bright, intense colors, such as pink or blue, can be very expensive due to their rarity.
- Cut: A good cut allows HPHT rough diamonds to show their full fire and luster, thus increasing their value. Cut grades include ideal cut, very good cut, good cut, etc. For example, an HPHT with an ideal cut will have a very good cut. For example, an HPHT rough diamond with an ideal cut will reflect the maximum amount of light, making it look more sparkling and will be priced higher accordingly.
- Brands and certificates: HPHT rough diamonds of famous brands usually have stricter quality control and after-sales service, and their prices are also affected by the brand premium. In addition, certificates issued by authoritative organizations, such as the Gemological Institute of America (GIA), the International Gemological Institute (IGI) and other certificates, can provide professional appraisal and assessment of the quality of HPHT rough diamonds, and the price of certificated rough diamonds will be more guaranteed than non-certificated ones, and their prices will be relatively higher.
- Market supply and demand: When demand for HPHT rough diamonds increases and supply is relatively low, prices will rise; conversely, when supply exceeds demand, prices may fall. For example, as consumer awareness and acceptance of cultivated diamonds increases, market demand continues to grow, and if production of HPHT rough diamonds does not increase significantly at this time, prices will tend to rise
