Buying Loose Moissanite: What to Check Before Setting It
Buying loose means choosing the stone and the setting separately — more control, and more of the risk on you. Six things decide whether the stone in the parcel fits the ring in your head: millimetres, ratio, depth, certificate match, batch colour, and who is responsible if the setter chips it.
Why buy loose at all
You want a setting nobody sells as a stock piece, so you buy a loose stone for a made-to-order mount. You are replacing a stone in an inherited ring — cheaper than remaking it, with an exact size match. Or you are building it yourself.
Millimetres, not carats
Carat is a weight. Settings hold a size. The gap between the two causes more failed projects than any other mistake.
Moissanite is less dense than diamond, so a moissanite and a diamond of the same diameter do not weigh the same — the moissanite is lighter. Sellers therefore quote "diamond equivalent" carats, meaning the weight of the diamond this would replace. Useful shorthand, terrible specification.
| Round diameter | Diamond-equivalent | Typical use |
| 4.0 mm | 0.25 ct | Studs, accents |
| 5.0 mm | 0.50 ct | Small solitaire, pendant |
| 6.5 mm | 1.00 ct | The standard engagement size |
| 8.0 mm | 2.00 ct | Large solitaire |
| 9.0 mm | 2.50–3.00 ct | Statement ring |
| 10.0 mm | 3.50 ct and up | Cocktail, dress ring |
The left column is what the prongs grip.
Shape and length-to-width ratio
For anything not round, the ratio of length to width defines the look more than carat weight does. A 1.30 oval reads classic; a 1.60 reads elongated and modern — same weight, different design.
- Oval — 1.30–1.40 classic, up to 1.60 for elongated
- Emerald and radiant — 1.40–1.50 classic
- Pear — 1.50–1.70, and check the shoulders sit symmetrically
- Marquise — 1.75–2.00, the most elongated common shape
- Cushion — 1.00–1.20, near-square to slightly long
"Oval, 8 × 6 mm" is a specification; "2 carat oval" is a hope.
Depth and girdle: the numbers that stop projects
Total depth decides whether the mount closes on the finger: a deep pavilion needs a high setting or an open gallery, and when you are re-stoning an existing mount, depth matters as much as diameter. Girdle thickness is what the prongs grip — a very thin girdle chips under a setter's pressure. Ask for both.
The certificate has to match this stone
A loose stone ships with its GRA card, and the card is worth nothing unless it describes the stone in the parcel. Check millimetres first, then weight, then shape. If the card says 8.00–8.05 mm and you measure 7.6 mm, the stone is not the stone on the card. Confirm the number appears on the invoice too.
Measuring it yourself
A $20 digital caliper is the best purchase a loose-stone buyer can make. Zero it first and check it against a known object, because they drift.
- Measure the diameter at three points about 60 degrees apart and average them. 8.02, 8.00, 8.04 is round; 8.05, 7.90, 8.00 is not.
- Measure depth with the depth rod, table to culet, without tilting the stone.
- Expect about 0.05 mm tolerance against the certificate.
Batch variation: the risk nobody mentions
If you are buying three stones for a three-stone ring, or replacing one of a pair, ask whether they came from the same batch. Coloured stones vary between production runs, and two stones that are both "champagne" can read different side by side. Order them together in one order and say they go into the same piece — a seller who cuts their own stones can pull matched pairs; a reseller cannot.
Why loose stones are often non-returnable
Loose stones are commonly final sale. Once a stone leaves the seller's control it can be swapped, chipped, dropped or set, and there is no way to prove which happened. A finished ring can be inspected as a whole; a loose stone's condition two weeks later is unverifiable.
So photograph stone and card together before unwrapping fully, and confirm return terms in writing before you pay. "Final sale" on a loose stone is normal — know it going in.
Handing your stone to a third-party setter
- The setter warrants the work, not the stone. Standard bench practice makes the jeweller responsible for their labour, not the customer's material. If a stone chips going into a prong, you usually own the loss.
- Ask what happens if it breaks, and get it in writing.
- Some setters refuse customer stones. That is an insurance position, not a red flag.
- Declare the value and take a written receipt describing the stone and its condition.
- Say what the stone is. Moissanite is hard but not indestructible, and a bench that mostly sets diamond will use different pressure. If it is a coated coloured stone, say that too — heat will ruin it.
You carry the stone, the setter carries the labour. Prefer a setter who has worked moissanite before.
What we make
We cut our moissanite in our own factory in Wuzhou, Guangxi, and have been doing it since 2008. We can quote exact millimetres, depth and ratio before you order, pull matched stones from the same batch when two or three must agree, and supply the GRA card for that specific stone with the number also on your invoice.
Loose stones and finished pieces sit within our $17–$2,020 range, most around $98, with settings in 925 silver, 9K, 14K and 18K gold. Shipping is free over $99 and $5.99 below, and unworn items in original packaging can be returned within 30 days. If you are re-stoning an existing ring, tell us the mount's stated capacity and we will confirm the fit before the stone ships.