Knowledge Base

Notes from the house.

A short library on the things that matter when choosing a stone, what the grades mean, how the diamond is made, and how shape changes everything.

Essay I

The 4Cs, plainly.

Every diamond is judged by four measures, established by the GIA in the 1950s and now used worldwide. They are not equal. Cut comes first.

Cut

Cut is the only C the diamond doesn't arrive with, it's earned by the cutter. Proportion, symmetry, polish: these decide how light enters the stone, bounces between facets, and returns to your eye. A poorly cut D-flawless diamond will look dull. A well-cut G-VS2 will outshine it.

We list cut grades the GIA way: Excellent, Very Good, Good, Fair, Poor. HOWDEN holds to Excellent and, occasionally, Very Good.

Color

Graded D (colorless) through Z (light yellow). The difference between D and G is invisible to almost everyone outside the trade, and invisible once set in white gold or platinum. We curate D, E, and F.

Clarity

A measure of internal inclusions and surface blemishes, viewed at 10× magnification. The scale runs FL (flawless) → IF → VVS1/VVS2 → VS1/VS2 → SI1/SI2 → I1/I2/I3. Anything VS2 or above is "eye-clean": no inclusions visible without a loupe.

Carat

Weight, not size. One carat is 0.2 grams. A round brilliant of 1.00ct measures roughly 6.5mm across the top; 2.00ct measures roughly 8.1mm , wider, but not double. Visual size grows with the cube root of weight, which is why a half-carat looks larger than its number suggests.

Essay II

How a lab diamond is grown.

A lab-grown diamond is a diamond. Same carbon lattice, same hardness, same refractive index, same fire. The only difference is where the carbon came from and how long it took.

The seed

Every cultivated stone starts with a thin slice of an existing diamond, the seed. From there, two methods take over.

HPHT, High Pressure, High Temperature

The seed is placed in a press with pure carbon and a metal flux. Pressure climbs to roughly 1.5 million pounds per square inch; temperature to 1,500°C. These are the conditions found 150km below the earth's surface. Carbon dissolves into the flux, migrates onto the seed, and crystallises. A few weeks later: a rough diamond.

CVD, Chemical Vapor Deposition

The seed is sealed in a vacuum chamber filled with a carbon-rich gas, usually methane. Microwaves ionise the gas into plasma. Carbon atoms rain down onto the seed, layer by atomic layer, in conditions closer to those found in interstellar space than under the earth. Slower than HPHT, with finer control over the result.

What arrives

Either method produces rough diamond crystal that is then cut and polished by hand, exactly as a mined stone would be. The finished diamond is graded by IGI or GIA, scored on the 4Cs, and laser-inscribed with its certificate number on the girdle.

There is no machine that can tell a lab diamond from a mined one without specialist instruments, because there is nothing chemical to tell apart.

Essay III

Choosing a shape.

Shape is the most personal decision in the process. It changes how the stone reads on the hand, what kind of brilliance it returns, and which settings will sit well with it. A short field guide.

Round Brilliant

The default for a reason. 57 facets engineered to maximise return of white light. Most forgiving of slight flaws, most expensive per carat, works in any setting.

Oval

The face-up size of a round brilliant in roughly 10% less weight. Elongates the finger. Watch for the "bow-tie", a dark band across the centre in a poorly cut oval.

Emerald

Step-cut, not brilliant, long parallel facets that act like a hall of mirrors. Less fire, more clarity. Demands a high clarity grade (VS1 or better) because every flaw is visible.

Cushion

A square or rectangle with rounded corners. Softer than a princess, warmer than a round. Pillowy in setting; suits vintage references and halos.

Pear

Brilliant-cut, asymmetric, round at one end, pointed at the other. Worn point-toward-the-nail. Like the oval, can show a bow-tie if cut shallow.

Princess

A square brilliant. Sharper, more modern than a cushion. Sets close to the finger; corners must be protected with V-tip prongs.

Marquise · Radiant · Asscher · Heart

Less common, more characterful. The marquise elongates the finger dramatically; the radiant balances brilliance with crisp lines; the asscher is the emerald's square cousin; the heart speaks for itself.

A practical rule: if you don't know, choose a round. If you know, choose what you've always quietly wanted.

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