Gemstone and Ring Scanning for CAD Remodelling: A Complete Guide

What is ring scanning for CAD remodelling?

CAD stands for computer-aided design. In jewellery it means building a ring as a precise 3D model on screen before any metal is cast. Remodelling is taking an existing piece, often an inherited engagement ring, a broken brooch or a drawer of odd earrings, and turning its stones and sometimes its metal into something new.

Scanning sits between the two. A 3D scanner records the shape of the original ring as millions of measured points, which the designer can bring straight into the CAD software. That gives you an exact digital copy of the shank (the band), the head (the part that holds the stone) and any engraving, so a new design can keep the parts you love and change the parts you don't. It also records the ring as it is today, which is a useful record before anything is cut apart.

The gemstones are a separate job. A scanner is very good at metal and poor at clear, faceted stones, so the stones are identified by a gemmologist, measured by hand and checked for damage. Only then does the designer know what can safely go into the new piece. Our guide to which parts of old jewellery can be reused safely covers that decision in more depth, and any unfamiliar term here is explained in the GemTrove jewellery glossary.

How does 3D scanning of a ring work?

Most jewellers use a desktop structured-light scanner. The ring sits on a small turntable while a projector shines a pattern of stripes onto it and one or two cameras watch how the stripes bend over the surface. Software turns those bends into distances, rotates the ring, repeats, and stitches dozens of views into one model. The finished file is usually saved as an STL (a mesh of tiny triangles) that CAD programs can read.

Polished gold and platinum act like mirrors, and mirrors confuse scanners. So the ring is usually given a very light coat of scanning spray, a fine matte white coating. Many modern sprays are sublimating, meaning they evaporate on their own within a few hours and leave nothing behind. Older powder sprays wipe or wash off. Either way, porous or treated stones should be protected or removed first, as covered below.

For almost every remodel, the structured-light scan plus careful hand measuring of the stones is all that is needed. CT scanning is mainly a research and museum tool.

Can gemstones be 3D scanned for a new setting?

Not reliably while they are clear and faceted. Light passes into a transparent gem, bounces off the back facets and comes back out somewhere else, so the scanner sees reflections rather than the surface. Spraying a stone matte solves the surface problem, but the scan still cannot see the pavilion (the lower part) while it sits deep in a setting, and the pavilion depth is exactly what the new seat has to fit.

So stones are measured by hand, ideally out of the setting. A gemmologist records:

• Length and width to 0.01 mm with a digital calliper, measured across the girdle (the stone's outer edge).
• Total depth from table (the flat top facet) to culet or point, which decides how tall the new head must be.
• Girdle thickness, because a very thin girdle is more likely to chip when claws are tightened.
• Outline and cut style, for example an old mine cut with a large culet, a native-cut sapphire that is lopsided, or a cabochon (a smooth domed stone with no facets).
• Existing damage: chips, abrasion on facet edges, open fractures and old repairs.

Old diamonds in heirloom rings are often cut very differently from modern ones, with smaller tables, taller crowns and an open culet, so they need deeper seats. Our comparison of how Old European and modern round cuts differ shows the proportions side by side, and the catalogue of every recognised diamond cut helps name the cut style correctly in the job notes.

Where a stone must stay set during the scan, for example a fragile opal the jeweller would rather not disturb, the designer models the visible crown from the scan and uses the hand measurements for everything else. Our guide to claw, bezel and other setting styles shows how each style grips a stone and how much room it needs.

Why identify the gemstone before remodelling?

Because the stone in an old ring is not always what the family story says, and the right handling depends on what it really is. A red stone might be ruby, garnet, spinel or a lab-created ruby. A blue one might be natural sapphire, lab-created sapphire, spinel or glass. Identification also reveals treatments such as oiling, fracture filling or glass filling, which change how the stone copes with heat, chemicals and an ultrasonic cleaner.

The main tool is a refractometer, which measures the refractive index (RI), how strongly a gem bends light. Each gem species has a narrow RI range. A gemmologist adds magnification, a polariscope and spectroscope where needed, then writes ID notes that travel with the stone into the job.

If a stone turns out to be lab-created, that is not a problem. It is real corundum or spinel, just grown rather than mined, and it reuses perfectly well. It simply needs to be described accurately from then on.

Families also ask where a stone came from. Older Australian rings often hold sapphires from the Central Queensland gemfields around Anakie and Rubyvale or from the New England district of NSW, and opals from Lightning Ridge, Coober Pedy or Andamooka. Origin can sometimes be suggested from inclusions and colour, but confirming it usually needs laboratory trace-element testing; our page on how laboratories work out where a gemstone was mined explains what is and isn't possible. If the ID reveals something unusual, such as a rare garnet variety, see our notes on rare and collector gemstones.

Which gemstones are safe to reuse in a new everyday ring?

A stone that sat quietly in a brooch for fifty years may not cope with life on a hand. Two properties matter. Hardness (the Mohs scale, 1 to 10) is resistance to scratching; household dust contains quartz at about Mohs 7, so softer stones dull over time. Toughness is resistance to chipping and breaking, which depends on cleavage (planes along which a crystal splits) and internal fractures. Our full Mohs hardness guide for gemstones covers the scale in detail.

These are general guides; a well-chosen setting changes the picture a great deal. An emerald in a low bezel can be worn far more freely than the same stone on tall claws. Our page on how long-wearing each gem is in an everyday ring goes stone by stone, and if a remodel is heading towards a coloured engagement ring, see choosing a coloured stone for an engagement ring.

How accurate is ring scanning for CAD remodelling?

A good desktop scanner records detail of roughly 0.01–0.03 mm, finer than a human hair, which is about 0.07 mm. That is more than enough to copy a shank profile, match an old engraving or design a band that sits flush against an existing engagement ring. But the scan is only one link in the chain. The final fit also depends on:

• Scanning spray thickness: a heavy coat adds a few hundredths of a millimetre; good operators use the thinnest even layer.
• 3D printing: resin printers used for jewellery commonly print in layers of about 0.025–0.05 mm, and the printed pattern is checked before casting.
• Casting shrinkage: metal shrinks slightly as it cools, often around 1–2%, and CAD files are adjusted to allow for it.
• Stone seats: the seat is usually modelled a fraction under size and finished by the setter with a burr, so the stone sits snugly without stress.
• Wear: an old ring is not the shape it left the workshop in. A scan shows exactly where the shank has thinned, often under the finger, and the new design can correct it.

Finger size is measured, not scanned. The scan gives the inside diameter of the old ring, but a wider new band fits more snugly than a narrow old one at the same size, so your finger should be checked on a sizing ring of similar width. Australian ring sizes use letters, and a whole letter size is roughly 0.4 mm of inside diameter (a half size about 0.2 mm).

What happens after the scan? From CAD file to finished ring

With the scan and the stone measurements in hand, the designer builds the new ring in CAD. The scanned mesh is used as a reference layer: the designer may keep the original head and redraw the shank, carry the old engraving onto a new band, or start fresh and simply use the stone measurements to build new seats. You usually see rendered images from several angles, with the millimetre widths of the band and the height of the stone above the finger.

Next, the model is 3D printed in resin so you can try it on. This is the moment to check proportions, comfort and how it sits beside other rings. Once approved, the pattern is cast in your chosen metal, cleaned up, polished, and the stones are set by hand. Old metal can sometimes be refined and reused, though mixed or unknown alloys often go to a refiner instead of being melted straight into the new piece.

After setting, stones need the right aftercare: some gems tolerate ultrasonic cleaning, others are damaged by it. Our cleaning and care notes for each gemstone are worth keeping with the new ring.

How much does ring scanning and CAD remodelling cost in Australia?

Pricing varies widely between jewellers and with how complex the design is. Scanning is often folded into the CAD design fee rather than charged separately. The ranges below are rough guides only, to help you understand where the money goes.

The biggest variables are metal weight (platinum and 18 ct gold cost much more than 9 ct), the number of small stones to set, and whether any stones need replacing. If a stone is too damaged to reuse, a replacement can be natural or lab-created; browsing the full range of coloured gemstones helps set expectations on colour and price. If you are swapping a centre diamond for a new shape, our overview of every diamond shape shows how each outline sits on the hand.

How to prepare your ring for scanning: step by step

1. Gather everything. Bring every piece you might reuse, including broken chains and single earrings; old metal and small stones add up.
2. Clean gently. Warm water, mild detergent and a soft brush. Skip the ultrasonic until the stones are identified.
3. Get the stones identified. Ask for written notes on species, natural or lab-created, treatments and any damage, for every stone.
4. Measure and assess. Have each stone measured to 0.01 mm and decide which are durable enough for the new design.
5. Scan the ring. The jeweller sprays it lightly (after removing or protecting porous stones), scans it and checks shank and claw wear.
6. Review the CAD renders. Check band width, stone height and how it sits with other rings; ask for changes now, not after casting.
7. Try on the resin print. Confirm comfort and finger size with a sizer of similar band width.
8. Approve casting and setting. Ask to keep the scan and the condition notes as a record of the original piece.

If you are still deciding on stone choice for the new design, our overview of how scratch-resistant each gem is and the everyday-ring durability comparison are useful to read side by side. And for broader inspiration, explore GemTrove's gemstone and birthstone guides.