Diamond basics
The 4 Cs, explained without the fog.
Cut, color, clarity, carat. The diamond industry teaches all four as if they're equally important. They're not. One of them is responsible for most of the sparkle, one is responsible for most of the price, and two are mostly for show. Here's the version your jeweler won't volunteer.
Most underrated. Hardest to fake.
Cut
Cut is the only "C" that's actually about how the diamond was made — the angles, polish, and proportions of the cuts on the stone. Color, clarity, and carat are about the rough material. Cut is the craftsmanship.
A poorly cut D/IF stone looks dull. A perfectly cut H/SI1 stone looks like it's lit from inside. GIA grades cut Excellent / Very Good / Good / Fair / Poor on round brilliants only — fancy shapes don't get a cut grade, only polish and symmetry. That's why fancy shapes price 15-25% lower than rounds at the same color and clarity.
Buy rule: Excellent or Very Good cut. Below that the stone looks dead and resells worse.
Most overrated by buyers. Priced super-linearly.
Carat
Carat is weight, not size. A 1.0ct round is about 6.5mm across the top; a 2.0ct is about 8.1mm — bigger, but not double. Yet a 2ct natural G/VS2 retails for ~$12,000 and a 1ct retails for ~$5,000. You don't pay double — you pay 2.5×.
The reason: large rough is exponentially rarer than small rough. A diamond cutter recovers about 50% of the rough weight when polishing, so producing a 2ct polished stone requires 4ct of clean rough. That kind of rough comes out of the ground much less often.
Save rule: Buy just under the popular size thresholds. A 0.95ct stone looks identical to 1.00ct face-up but costs 15-20% less. Same for 1.45ct vs 1.50ct, 1.95 vs 2.00ct.
Visible past J. Below H, you can usually save money.
Color
GIA grades diamond color D (colorless) through Z (light yellow). D-F are colorless, G-J are near-colorless, K and below show visible warmth. Most non-jewelers can't tell D from G when the stone is in a setting.
Yellow gold settings hide warmth. Platinum and white gold reveal it. So a G in white gold looks identical to a D in white gold; an H in yellow gold looks identical to an E in yellow gold.
Save rule: G-H in white metal, I-J in yellow metal. You'll never notice the difference, and you save 10-25% over D-F.
Sounds important. Mostly invisible without a loupe.
Clarity
Clarity grades the inclusions inside the stone, viewed at 10× magnification. FL/IF (no inclusions visible at 10×) are the rarest. VS1/VS2 inclusions are invisible to the naked eye. SI1/SI2 inclusions are sometimes visible if you know exactly where to look. I1/I2/I3 inclusions are visible to anyone.
The clarity-grade increments are bigger than they look. FL → IF is essentially nothing in real-world appearance but adds 20% to the price. VS2 → SI1 is also nothing visible to the naked eye but saves 15-20%. The cliff is at SI2 → I1, where inclusions start being visible.
Save rule: "Eye-clean SI1" or VS2. Below that you start to see things; above that you're paying for invisible-to-everyone perfection.
If you have to compromise on one C, compromise on clarity.
Cut is the only C that affects how the diamond actually looks at arm's length. Color and clarity affect how it looks under a loupe. Carat affects price more than appearance. The cheapest beautiful diamond is an Excellent-cut, G-H, SI1 — and it'll look identical to the D/FL stone next to it on the same finger.