A lab grown diamond is made by recreating, in a controlled laboratory, the conditions that form a diamond in the earth. There are two methods. High pressure high temperature, known as HPHT, places a small diamond seed in extreme heat and pressure alongside carbon, which crystallises around the seed. Chemical vapour deposition, known as CVD, places a seed in a chamber filled with a carbon rich gas, which is heated until carbon atoms settle onto the seed layer by layer. Either way the result is a single diamond crystal, grown over a few weeks rather than billions of years. The rough stone is then cut and polished exactly like a mined diamond. The finished diamond has the same carbon structure, the same hardness and the same optical properties as a natural one. The process is the only thing that differs. The material is identical.
Read the about lab grown diamonds page for more on the science and how we use it at Luma.
HPHT in more detail
HPHT mimics the conditions deep in the earth's mantle. A diamond seed is placed in a press alongside pure carbon, then subjected to temperatures over 1,400 degrees Celsius and pressures around 60,000 atmospheres. The carbon dissolves into a molten metal flux and recrystallises onto the seed, building up a rough diamond in a few weeks.
CVD in more detail
CVD works differently. A thin diamond seed sits in a vacuum chamber filled with a carbon rich gas, usually methane and hydrogen. Microwave or plasma energy breaks the gas apart, and carbon atoms settle onto the seed layer by layer, building a rough diamond crystal. CVD is the more commonly used method today for gem quality stones.
From rough to finished diamond
Once grown, the rough crystal is cut and polished by experienced cutters using the same techniques and equipment used on mined rough. The finished diamond is graded by an independent laboratory, most often IGI or GIA, and issued a certificate stating its carat, cut, colour, clarity and the fact that it is lab grown.
Related questions
How long does it take to grow a diamond?
A few weeks to a couple of months depending on the size, method and quality. A rough one carat finished stone typically grows in around four weeks.
What is a diamond seed?
A small slice of diamond used as the starting point for growth. The new diamond atoms attach to this seed in the same crystal pattern, extending it outwards.
Are HPHT and CVD diamonds different in quality?
Both methods produce gem quality diamonds. The differences are in trace inclusions and growth patterns that gem labs use to identify the method, not in the diamond's appearance or durability.
