Diamond Jewelry

Cut, colour, clarity and carat weight - the standard framework for describing a diamond, developed so that stones could be compared consistently.

Cut describes how well the stone's proportions return light. Colour grades how close to colourless it is. Clarity describes internal and surface features. Carat is the stone's weight.

They are a description rather than a ranking. The most useful way to use them is to decide which matters most to you and spend there, rather than trying to maximise all four.

Cut, by a clear margin, because it is the one you can see. Cut determines whether a diamond gathers light and returns it as brilliance or lets it leak away and look flat.

A well-cut stone at a modest colour and clarity grade will consistently look better than a poorly cut one with superior numbers on a report.

Colour and clarity are where most people over-buy, because both scales continue well past the point where an unaided eye can tell the difference.

Yes. A laboratory-grown diamond has the same carbon crystal structure, the same hardness of 10 on the Mohs scale, and the same optical properties as a mined diamond. It is graded on the same four Cs by the same laboratories.

It is not a simulant. Cubic zirconia and moissanite are different materials that resemble diamond; a lab-grown diamond is diamond.

The differences are practical rather than physical: lab-grown stones generally cost less for a given specification, while natural stones carry geological rarity and an established resale market. Each listing states which a piece uses.

The useful target is eye-clean - a stone with no inclusions visible to an unaided eye at normal viewing distance. Grades above that line are describing things only a loupe reveals.

Where the line falls depends on the stone. A larger diamond shows more than a small one, and an open step cut like an emerald cut shows more than a brilliant cut, which breaks light up and hides features.

For most buyers, choosing an eye-clean stone and putting the saving into cut produces a better-looking piece than buying a higher clarity grade would.

Considerably, and this is one of the most useful things to know. Yellow gold masks warmth in a diamond, so a stone in the near-colourless range set in yellow gold looks perfectly white.

Platinum and white gold do the opposite: a cool white metal beside a warmer stone makes the warmth more noticeable.

So the sensible approach is to match the two. A slightly lower colour grade in yellow gold often looks identical to a higher grade in platinum, for a meaningful difference in price.

It is the combined weight of every diamond in a piece, including all the accent stones, rather than the weight of any single stone.

On a halo, a cluster or a pavé band, the total carat weight can be spread across dozens of small stones. A one-carat total weight in thirty stones is a very different object from a one-carat solitaire.

Where a design has a distinct centre stone, its individual weight is usually given separately. Reading which figure is which is the most important thing on a diamond listing.

Because carat measures weight, not dimensions. A shallow-cut stone spreads its weight across a wider face and looks larger from above; a deep-cut stone hides weight underneath where you cannot see it.

Shape plays a part too. Elongated cuts such as marquise, oval and pear generally read larger than a round stone of the same weight, because more of their surface faces upward.

Millimetre dimensions describe what you will actually see, which is why listings state them alongside the weight.

Diamond is the hardest natural material, at 10 on the Mohs scale, so it resists scratching better than anything else you could wear.

Hardness is not the same as toughness, though. Diamond has cleavage planes, and a sharp blow at the right angle can chip a stone - most often at an exposed point on a marquise, pear or princess cut.

In practice the setting fails long before the stone does. Prongs wear with use, and having them checked periodically is the single most effective thing you can do to keep a diamond where it belongs.

Some diamonds glow, usually blue, under ultraviolet light. It is a natural characteristic rather than a treatment or a defect, and a substantial share of diamonds show it to some degree.

In most cases it is invisible in normal lighting and has no effect on how the stone looks. In a warmer-coloured stone, faint blue fluorescence can even make it appear slightly whiter.

Very strong fluorescence occasionally gives a stone a hazy or milky appearance, which is worth avoiding, but moderate fluorescence is a non-issue and often means a lower price for an identical-looking diamond.

Warm water with a little mild soap and a soft brush, working underneath the setting where residue collects. Rinse well and dry with a soft cloth.

Diamonds attract grease, which is why a stone that looked brilliant in a shop can look dull after a few weeks of wear. Cleaning underneath the stone, not just on top of it, is what restores the brightness.

Have the setting checked periodically. Prongs are the part that wears, and tightening one is far cheaper than replacing a lost stone.