The most expensive misunderstanding in jewellery is the belief that a diamond twice the weight costs twice the money. It does not, it never has, and knowing why is worth several thousand pounds.
Price per carat, not price
The trade does not quote a price for a stone. It quotes a price per carat, and then multiplies. A 0.50ct stone at £4,000 per carat is £2,000; a 1.00ct stone at £7,000 per carat is £7,000. The weight doubled, the price per carat also rose, and the total more than tripled.
Price per carat climbs because large pieces of clean rough are rare, and rarity compounds. Roughly speaking it steps at 0.30, 0.50, 0.70, 0.90, 1.00, 1.50, 2.00 and 3.00 carats — the weights that people ask for by name.
How each C moves the number
Indicative orders of magnitude, holding everything else constant:
| Change | Rough effect on price | Visible to the eye? |
|---|---|---|
| Excellent cut → Good cut | −15 to −25% | Yes — immediately |
| D colour → G colour | −15 to −25% | Rarely, once set |
| G colour → J colour | −15 to −20% | Sometimes, against platinum |
| VVS1 → VS2 | −15 to −25% | No |
| VS2 → SI1 (eye-clean) | −10 to −20% | No, if hand-picked |
| 1.00ct → 0.90ct | −15 to −20% | No |
| None → Strong fluorescence | −5 to −15% | Occasionally, in sunlight |
Stack the three invisible savings — colour to G or H, clarity to eye-clean SI1, weight just under the milestone — and you are routinely forty per cent below the headline stone with no visible difference on a hand. That is the whole game, and it is why the 4Cs are worth learning.
What UK budgets realistically buy
Round brilliant, natural, Excellent cut, hand-selected eye-clean. Centre stone only; a setting adds roughly £600 to £2,500 depending on metal and complexity. These are indicative ranges at the time of writing and move with the market.
| Budget (stone only) | Realistic weight | Typical grades |
|---|---|---|
| £1,500 – £2,500 | 0.40 – 0.55ct | G–H, SI1 |
| £2,500 – £4,500 | 0.60 – 0.80ct | G–H, VS2–SI1 |
| £4,500 – £8,000 | 0.90 – 1.10ct | G–I, VS2–SI1 |
| £8,000 – £15,000 | 1.20 – 1.60ct | F–H, VS1–VS2 |
| £15,000+ | 1.70ct and above | D–G, VVS2–VS1 |
By appointment · Hatton Garden
Tell us the number, not the stone
Give us a budget and a shape and we will come back with three genuinely different options and the reasoning behind each. It is a far better conversation than walking a street comparing windows.
Where the money actually goes
For a typical certificated stone sold on Hatton Garden, the rough division looks something like this: the rough diamond itself is the largest single component; cutting and polishing take a significant slice, and a better cut costs more because it sacrifices weight; laboratory grading adds a fixed fee per stone; then dealing margins, retail overheads, the mount, the setter’s labour, hallmarking, insurance and VAT.
Two consequences worth knowing. First, VAT is charged on the whole thing in the UK, so a fifth of what you pay is tax — which is why like-for-like comparisons with overseas prices are usually meaningless. Second, the cheapest place to save is never the setting: a badly made mount costs a fraction and loses you the stone.
Lab-grown prices behave differently
Laboratory-grown diamonds are chemically and optically diamond, and they are graded on the same scales. Their pricing, though, follows manufacturing rather than scarcity, and manufacturing costs fall. Over the past few years grown-stone prices have dropped sharply and continue to.
That makes them excellent value for size today and a poor store of value tomorrow. If the priority is the largest, cleanest stone your budget can reach, grown is a rational choice — buy it with open eyes and a report that says so. If the piece is meant to be handed on, natural behaves more like the asset people assume jewellery to be. We sell both and we will tell you which we would choose and why.
Three ways people overpay
- Buying the milestone. Insisting on the words “one carat” rather than the appearance of one carat.
- Buying clarity nobody will see. Paying VVS prices for a stone that will be viewed at arm’s length for the rest of its life.
- Buying a description instead of a stone. Comparing “1ct G VS1” across shops without comparing cut grade, proportions, laboratory and fluorescence. Those four lines are where the price difference lives.
A fair test of any quotation
Ask for it in writing, itemised between stone and mount, with the laboratory and report number for the stone. If all three arrive without friction, you are dealing with someone who expects to be compared — which is exactly who you want to buy from on this street.
By appointment · Hatton Garden
An honest number, in writing
We quote stone and mount separately, name the laboratory, and put the report number on the paperwork. Compare it with anything else on Hatton Garden — that is rather the point.
Written on Hatton Garden. Grading terminology follows GIA definitions; prices are indicative at the time of writing and move with the market. Nothing here is a valuation.
