Coloured stones are priced by appearance rather than by a numeric grade, which makes them harder to specify than diamonds. Lab grown material removes the largest commercial risk: it can be produced to a consistent colour, so a suite or a bracelet run can actually match.
Stone-by-stone reference
| Stone | Hardness | Refractive index | Specific gravity | Specification focus |
|---|---|---|---|---|
| Emerald | 7.5–8 | 1.57–1.58 | 2.67–2.78 | Colour saturation, eye-clean clarity, no fracture filling |
| Ruby | 9 | 1.76–1.77 | 3.97–4.05 | Tone and saturation; avoid brown modifier |
| Sapphire | 9 | 1.76–1.77 | 3.95–4.03 | Evenness of colour across the parcel |
| Paraiba tourmaline | 7–7.5 | 1.62–1.64 | 3.06 | Neon cyan saturation; copper-bearing tone |
| Padparadscha sapphire | 9 | 1.76–1.77 | 3.95–4.03 | Pink–orange balance; neither dominates |
| Zircon | 7.5 | 1.92–1.98 | 4.6–4.7 | Blue and white calibrated melee |
Why calibration decides whether you can build sets
Calibrated sizes — 5×3 mm ovals, 4 mm rounds, 6×4 mm cushions — let you assemble matched suites, halos, bracelets and earring pairs without hand-sorting. Specify calibrated sizes with a tolerance in tenths of a millimetre and require the parcel sorted by size band rather than delivered as a mixed lot.
Colour consistency: the single biggest advantage of lab grown
- Establish a colour standard — retain a reference stone or a photographed master set — before the first production run.
- Confirm the standard on the approval sheet, with photographs under daylight and under a colour-corrected lamp.
- Require every subsequent run to be matched against the retained standard, not against a new production batch.
- Record the standard on your own purchase orders so a change of supplier still has a benchmark.
Care and wear guidance
- Emerald: avoid ultrasonic and steam cleaning; use warm water with mild soap and a soft brush. Not ideal for everyday rings without protective setting.
- Ruby and sapphire: robust for daily wear; ultrasonic cleaning is acceptable.
- Paraiba tourmaline: beautiful but relatively soft; best in earrings, pendants and protected settings rather than constant-wear rings.
- Padparadscha sapphire: corundum hardness, suitable for bridal.
Treatments and disclosure
Ask four questions of any coloured stone supplier: is the material as-grown or treated; is there fracture filling, oiling or dyeing; does your market require disclosure of that treatment; and will the same treatment status hold for a reorder in six months. Consistency of disclosure matters more than the absence of treatment — buyers can sell a disclosed treated stone, but not a surprise.
Specification template
Stone: lab grown emerald, vivid bluish green, eye clean, oval 6×4 mm calibrated ±0.1 mm, no fracture filling, IGI report on request; metal: 18K yellow gold, 2.4 g ±5%; setting: four-prong; MOQ 10 pcs; lead time 12–18 days.
Setting coloured stones without losses
Coloured stones vary in toughness even at similar hardness, and setting is where most damage happens. Three practical rules: use protective settings (bezels or heavy prongs) for emerald and paraiba, avoid heat-intensive soldering near the stone, and set softer stones last in a multi-stone piece. For bracelets and rings that see daily wear, prefer corundum — ruby and sapphire — over emerald and tourmaline regardless of hardness figures on paper.
Building a colour programme that sells
- Start with one or two stone types rather than a broad palette; depth beats breadth when you are establishing a look.
- Fix a colour standard with a retained reference stone and photographs under two lighting conditions.
- Order calibrated sizes so you can build suites and matched pairs from stock rather than hand-sorting.
- Price the metal separately from the stone so you can explain a price change to your own customer.
- Test the coloured line in earrings and pendants before committing to rings, where wear risk is highest.
Care instructions worth printing on the card
Emerald and paraiba: warm water, mild soap, soft brush, no ultrasonic or steam. Ruby, sapphire and padparadscha: ultrasonic cleaning is acceptable; avoid sudden temperature change. All coloured stones: remove before swimming, cleaning with chemicals or heavy manual work. Printed care cards cost very little and materially reduce the returns that come from customers cleaning the wrong stone the wrong way.