Lab-grown diamonds are made by growing real diamond crystals from carbon in a controlled lab, usually using one of two main methods: HPHT (High Pressure High Temperature) or CVD (Chemical Vapor Deposition). Both approaches start with a tiny diamond “seed” and build a larger crystal over days to weeks.

What exactly is a lab-grown diamond?

  • It is pure crystallized carbon with the same crystal structure, hardness, and brilliance as mined diamonds.
  • Chemically, physically, and optically, it behaves like a natural diamond; the difference is where it forms (lab vs deep underground).
  • Labs can tweak growth conditions to influence color and clarity, which gives more control than nature.

Method 1: HPHT – “pressure-cooking” carbon

HPHT is the older, very intense method that imitates the deep Earth: very high pressure plus very high temperature.

Basic HPHT steps

  1. A tiny diamond seed is placed in a press with a carbon source (often graphite) and a metal flux made of metals like iron, nickel, or cobalt.
  1. The capsule is squeezed to pressures of up to tens of thousands of atmospheres and heated to around 1,300–1,600 °C.
  1. Under these conditions, the carbon dissolves into the molten metal and then crystallizes onto the seed, layer by layer, forming a diamond.
  1. Growth can take from several hours to a few weeks depending on the size and quality targeted.

What comes out

  • The rough crystal is removed, then cut and polished just like a mined stone.
  • HPHT is commonly used for smaller stones or for certain colors, and also to treat/improve color in some diamonds.

Method 2: CVD – growing diamond from gas

CVD is a newer, very popular technique that grows diamond from a carbon-rich gas inside a chamber.

Basic CVD steps

  1. A thin diamond seed plate is placed in a vacuum chamber and heated to roughly 800–900 °C.
  1. The chamber is filled with carbon-rich gases, often methane mixed with hydrogen and sometimes other gases.
  1. Microwaves, lasers, or hot filaments turn the gas into plasma, breaking apart the molecules so carbon atoms can settle onto the seed.
  1. Carbon atoms bond in the diamond crystal structure and build a new diamond layer by layer over days or weeks.

What comes out

  • The result is a flat diamond “slab” that can be sliced, then cut into individual gems and polished.
  • CVD is favored for high-clarity, colorless or near-colorless stones, and labs can adjust gas mix and conditions to control growth.

Are they really “real” diamonds?

  • Both HPHT and CVD diamonds have the same hardness (10 on Mohs), refractive index, and density as mined diamonds.
  • Gem labs can usually tell them apart using advanced instruments, but to the eye and in normal wear they behave the same.
  • Many jewelers now sell both, and lab-grown stones are a big part of current diamond industry debates and forum discussions about ethics, price, and tradition.

Quick Scoop summary

  • Two main methods: HPHT (high pressure + high heat) and CVD (carbon plasma gas in a chamber).
  • Both start from a small diamond seed and add carbon until a full-size crystal grows.
  • The finished stones are cut and polished like mined diamonds and have the same core properties, with more control over quality and usually a lower environmental and social footprint according to many recent discussions.

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How do they make lab grown diamonds? Learn how HPHT and CVD technologies grow real diamonds from carbon seeds in modern labs, plus what recent discussions say about these gems. Information gathered from public forums or data available on the internet and portrayed here.