Carat Weight vs Size

Moissanite is lighter than diamond, so carat weight doesn't directly correspond to visual size. Learn how to compare stones accurately.

Why Carat Weight Differs

Moissanite has a specific gravity of 3.22, while diamond is 3.52. This means a moissanite of the same diameter weighs approximately 10-15% less than a diamond. A 6.5mm moissanite weighs ~0.88ct but looks like a 1ct diamond.

Size Comparison Chart

TABLE:

Diameter (mm)	Diamond Equivalent	Moissanite Actual Weight
5.0mm	0.5ct	0.44ct
6.0mm	0.8ct	0.70ct
6.5mm	1.0ct	0.88ct
7.5mm	1.5ct	1.32ct
8.0mm	2.0ct	1.76ct

How Holycome Lists Stones

We list both diamond equivalent size (mm diameter) and actual moissanite carat weight to avoid confusion. This ensures customers know exactly what they're getting.

Pricing by Size vs Weight

Moissanite is typically priced by size (mm) rather than weight, since visual size is what matters for jewelry. This makes comparison shopping easier for customers.

Stone Grades Buyers Can Actually Audit

Moissanite is graded on colour, clarity and cut in the same language as diamond, which makes it easy to compare across suppliers. Ask for the colour grade in writing (D-E-F near-colourless versus G-H-I near-colour) and request a photo of the actual parcel under neutral light, not a studio hero shot.

GRA or IGI documentation should travel with every parcel and list carat weight, colour and cut. Pass the certificate to your end customer: a documented stone converts better at retail and reduces returns from buyers who expected diamond grading.

Cut is where cheap parcels hide. A shallow pavilion cut loses fire under indoor light, so ask for an Ideal or Excellent cut grade and check a loose stone against a white card before you commit to 500 pieces.

Sourcing Benchmarks for This Category

Buyers usually benchmark three numbers before they shortlist a supplier: unit cost at a fixed volume, sample lead time, and the reject rate they can absorb without hurting sell-through. Get all three in writing, because a low unit price with a 12% reject rate is more expensive than a mid price with a 3% reject rate.

For stock designs HOLYCOME quotes from 50 pieces per design. Samples leave Wuzhou in 3 to 5 days. Bulk production runs 15 to 20 days under 500 pieces, and custom molds run 25 to 30 days. Payment is 30% T/T deposit with the balance against the bill of lading, and sample costs are credited back on the bulk order.

Ask for the cost breakdown line by line: metal weight, stone cost, labor, plating and packaging. Suppliers who will not break out metal weight are usually padding the labor line, and you cannot negotiate what you cannot see.

How the Production Line Actually Runs

The process starts with CAD. Your sketch, reference photo or existing sample is modelled to scale, and a 3D render comes back for approval. Nothing is cast until you sign off, which is where most quality problems are avoided.

From the approved model the factory cuts a wax or resin pattern, casts the piece, then sets stones by hand. Setting is the step that decides whether a ring looks like a $40 piece or a $400 piece: prongs must be even, seats must be flush and no stone should sit proud of the surface.

After setting, pieces go through polishing, plating and a final inspection under 10x magnification. Rejects are pulled at that station, not at packing, so a clean carton is a sign the QC step is real rather than a formality.

Quality Control You Should Specify

Write your acceptance criteria into the purchase order instead of relying on a verbal promise. The usual baseline is 3 to 5% dimensional or setting defects under 10x loupe, with defective units replaced free in the next shipment.

For plated goods, specify plating thickness and ask for a salt-spray result. One to two micron PVD over 316L holds colour for 12 to 18 months of daily wear; thin flash plating fails within weeks and comes back as refund requests.

For stone-set goods, add a stone-retention check: press each stone lightly and reject any that moves. A single lost stone costs more in goodwill than the whole piece costs to make.

Packing, Shipping and Paperwork

Packing protects margin. Each piece goes into an anti-tarnish bag with a sulfur absorber, then a labelled inner box, then a master carton with a packing list that matches your SKU codes. Mixed size and colour runs are packed and labelled separately so your receiving team does not have to re-sort.

Shipments leave through Guangzhou or Shenzhen. DDP is convenient for a first order because the landed cost is fixed; DAP is cheaper once you have your own customs broker. Either way, confirm the HS code and origin declaration before the carton seals.

Keep the commercial invoice, packing list and any certificate of origin in one folder per shipment. If your marketplace or a customs broker asks for documentation six months later, that folder is the difference between a routine answer and a delayed shipment.

Frequently Asked Questions

Why is moissanite lighter?

Silicon carbide (moissanite) has a lower density than pure carbon (diamond), so the same volume weighs less.

Should I buy by carat or mm?

For jewelry, buy by mm size — that's what you see. Carat weight is secondary for moissanite.

Conclusion

Understanding the size-weight relationship helps you and your customers make informed choices. Holycome provides both measurements for every stone. Contact service@holycome.com for our stone selection guide.

For third-party reference, the Wikipedia article on moissanite details moissanite’s discovery, optical properties and use in jewellery.

Carat Weight vs Size: Understanding Moissanite Measurements