What are Chemical Vapor Deposition (CVD) and High Pressure High Temperature (HPHT) methods for creating synthetic diamonds?

• CVD Method: CVD, a diamond seed is placed in a vacuum chamber with a carbon-rich gas mixture, typically methane and hydrogen. Under high temperatures and low pressure, carbon atoms deposit on the seed, gradually building up the diamond.
• HPHT Method: HPHT involves subjecting a diamond seed to extreme pressure and temperature conditions, replicating the natural formation process of diamonds in the Earth's mantle.