CVD Diamonds

CVD diamonds — short for Chemical Vapor Deposition — are one of the two main types of lab-grown diamonds on the market today (the other being HPHT, High Pressure High Temperature). CVD is the newer of the two methods and now dominates production of high-clarity, high-color gem-grade lab-grown diamonds. This guide explains how CVD diamonds are made, how they compare to mined and HPHT diamonds, and what to look for when buying one.

In short: CVD (Chemical Vapor Deposition) is one of two methods for producing lab-grown diamonds — the other being HPHT. CVD grows diamonds atom-by-atom from carbon-rich plasma over 2-4 weeks per 1-carat stone. The result is chemically and optically identical to mined diamond, graded the same way by GIA/IGI, and priced 60-70% lower. Most D-IF and high-clarity lab-grown diamonds on the market are CVD; HPHT is more common in fancy yellows.

How CVD diamonds are made

CVD growth starts with a small diamond seed — a thin slice of either lab-grown or mined diamond, typically 3–5 millimeters across. The seed is placed in a sealed reactor chamber and the chamber is filled with a carbon-rich gas mixture, usually methane and hydrogen. The gas is energized with microwaves until it forms a plasma, breaking the methane molecules apart. The freed carbon atoms then deposit onto the seed crystal layer by layer, building a new diamond on top of the seed at roughly 0.1 millimeters per hour. A 1-carat round brilliant takes about 2–4 weeks to grow.

CVD vs HPHT diamonds

HPHT (High Pressure High Temperature) recreates the geological conditions of the earth's mantle — pressure of around 60,000 atmospheres at 1,500°C — forcing carbon to crystallize into diamond around a seed in days. HPHT diamonds tend to have slightly more inclusions and often have a yellowish or brownish cast that requires post-growth treatment. CVD diamonds grow at much lower pressure, producing fewer inclusions and a more consistent color profile. Most D-IF and D-VVS quality lab-grown diamonds sold today are CVD; HPHT is more common in lower-color grades and fancy yellows.