The same atom, different origin
Every diamond — mined or grown — is the same thing: carbon atoms arranged in a crystal lattice. The arrangement is what gives diamond its hardness (10 on the Mohs scale), its refractive index (2.42), and its fire (the way it splits white light into spectral colours).
The only question is where that arrangement happens. Underground, under volcanic pressure? Or in a chamber, under controlled conditions?
The diamond doesn't care. Physics doesn't either.
A diamond is a structure, not a story. The structure is identical.
The CVD process
Chemical Vapour Deposition is how Zei's diamonds are grown. It's the more modern of two lab methods (the other being HPHT — High Pressure High Temperature). Here's how it works:
Step 1: The seed
A thin slice of existing diamond — about 300 microns thick, roughly the width of three human hairs — is placed in a vacuum chamber. This is the seed crystal. Its atomic lattice provides the template for new growth.
Step 2: The gas
The chamber is filled with a carbon-rich gas, typically methane (CH₄), mixed with hydrogen. The chamber is sealed and the pressure is reduced to below atmospheric.
Step 3: The plasma
Microwave energy is used to heat the gas to approximately 1,500°C. At this temperature, the gas molecules break apart. Carbon atoms separate from hydrogen atoms and form a plasma — a superheated ionised gas.
Step 4: The growth
Free carbon atoms drift downward and land on the seed crystal. Because the seed's lattice is already arranged in a diamond pattern, the new carbon atoms lock into the same structure. Layer by layer, atom by atom, the diamond grows.
Growth rate: approximately 0.1 to 10 microns per hour, depending on conditions. A 1-carat rough crystal takes roughly 6 to 8 weeks.
Step 5: The reveal
When the rough crystal reaches target size, the chamber is cooled and opened. The result is a rough diamond — cloudy, angular, and unmistakably real. From here, it goes through the same cutting and polishing process as any mined rough.
What about HPHT?
High Pressure High Temperature simulates the conditions that create diamonds underground: extreme pressure (roughly 5 GPa) and temperatures above 1,400°C. A carbon source (usually graphite) is pressed between metal catalysts until it crystallises.
HPHT diamonds are perfectly real, but CVD has become the preferred method for gem-quality stones because:
- ◇Better colour control — CVD produces consistently D–F colour without post-growth treatment
- ◇Fewer metallic inclusions — HPHT uses metal catalysts that can leave traces
- ◇Larger sizes — CVD can grow larger rough stones more efficiently
- ◇Lower energy — CVD chambers use less energy than HPHT presses
How do we know it's the same?
Because we can measure it. A CVD diamond and a mined diamond have:
- ◇Identical crystal structure — face-centred cubic (Fd3m space group)
- ◇Identical hardness — 10 on the Mohs scale
- ◇Identical refractive index — 2.417
- ◇Identical thermal conductivity — ~2,200 W/mK
- ◇Identical density — 3.51 g/cm³
The only detectable difference is trace growth markers — subtle patterns in fluorescence that specialised lab equipment (not the naked eye, not a jeweller's loupe) can identify. This is how grading labs like the IGI certify a stone's origin.
The grading is identical
Every Zei diamond is graded by the International Gemological Institute (IGI) using the same 4C criteria applied to mined stones:
- ◇Carat — weight
- ◇Cut — proportions, symmetry, polish
- ◇Colour — D (colourless) to Z (light yellow)
- ◇Clarity — FL (flawless) to I3 (included)
Our tennis bracelets use D–F colour, VVS1–VVS2 clarity stones. These grades sits in the top tier of the grading scale — regardless of origin.
The energy question
A common concern: does growing diamonds in a lab use a lot of energy?
Yes, it uses energy. A CVD chamber runs continuously for weeks. But context matters:
- ◇Mining a single carat of diamond moves roughly 250 tonnes of earth
- ◇CVD growth of a single carat produces approximately 0.028 grams of carbon emissions (when powered by renewable energy)
- ◇Most modern CVD facilities, including those in our supply chain, run on renewable or offset energy
The comparison isn't close.
Same atom. Same structure. Same brilliance. Different origin. That's it.
