Cut
How well the stone is proportioned and polished to return light. It does the most for sparkle, so it is the one not to give up.
- Excellent
- Very good
- Good
- Fair
- Poor
Stay in the top two.
Fine jewellery. Personal service.
Diamond guide
Choosing a diamond, in plain words.
Shape first, then the four Cs, then the metal and the size. Five minutes end to end, or jump to the part you need.
Shape
The outline of the stone, and the first thing anyone sees. Choose it before anything else: it decides how the other choices look.
- Round Returns the most light. The classic.
- Oval Long and soft; looks larger for its weight.
- Emerald Long steps and clear windows. Calm, architectural.
- Pear A teardrop, usually worn point to the nail.
- Princess A square with a brilliant’s sparkle.
- Cushion A softened square with warm, old-fashioned fire.
- Marquise A long boat shape; covers the most finger.
- Radiant Cut corners, brilliant sparkle.
- Asscher A square step cut, like a hall of mirrors.
- Heart Reads best from about a carat up.
The four Cs
Cut, colour, clarity and carat: the four things a gem lab grades. Cut matters most; the other three are where the budget is balanced.
Colour
How free of tint the stone is, from D, with none, down the alphabet towards light yellow. In yellow or rose gold, a stone from G to J looks as white as a D.
- D
- E
- F
- G
- H
- I
- J
- K
- L
- M
Clarity
How few marks are inside the stone. Below VS2 most marks cannot be seen without a loupe; what matters is whether the stone is clean to the eye.
- FL
- IF
- VVS1
- VVS2
- VS1
- VS2
- SI1
- SI2
- I1
Usually clean to the eye from VS2, and in a good SI1.
Carat
Weight, not size: one carat is a fifth of a gram. A well-cut stone looks larger than a deep one of the same weight. Round stones from above, to scale:
- 0.5 ct 5.2 mm across
- 1 ct 6.5 mm across
- 1.5 ct 7.4 mm across
- 2 ct 8.2 mm across
- 3 ct 9.4 mm across
Lab-grown or natural
Both are diamond. What differs is where and how fast they formed, and the price.
The same
- A crystal of carbon, the hardest natural material
- The same light and fire
- Graded on the same four Cs
Different
- Grown above ground in weeks, not underground over ages
- A lower price for the same size and grade
- Origin: every piece’s page says which it is
Grading reports
A grading report is a gem lab’s independent record of a stone: its four Cs, its measurements and any treatment. Where a stone has one, its page names the lab.
Ask for a report numberMetal
The pieces here are set in 14k or 18k gold. 18k is richer in colour and a little softer; 14k is harder-wearing for every day.
Ring size
Measure a ring that fits the same finger against a size chart, at the end of the day when fingers are largest. Between two sizes, choose the larger.
More on sizingBefore you go
Still deciding?
Talk it through with a jeweller, or find the answer yourself. Four ways in.