Gold, Diamonds, and Gemstones: How Each Is Assessed in a Buy Appraisal

Gold

Gold is the most straightforward category to assess, because the foundation of the valuation is objective and publicly available: the spot price.

What Is the Spot Price?

The gold spot price is the current global market price for one troy ounce of pure gold. It changes throughout every trading day, influenced by currency movements, inflation expectations, geopolitical events, and global demand. You can check it on any financial news site at any time.

When a buyer assesses gold jewellery, the spot price is the starting point — but only the starting point.

Purity

Gold jewellery in Australia is most commonly found in three purity levels:

• 9ct gold — 37.5% pure gold, 62.5% other metals

• 18ct gold — 75% pure gold, 25% other metals

• 24ct gold — 99.9% pure gold (rare in jewellery; more common in bullion)

The purity of a piece directly determines how much of its weight is actual gold. A 9ct gold chain weighing 10 grams contains 3.75 grams of gold. An 18ct chain of the same weight contains 7.5 grams. At the same spot price, the 18ct piece is worth approximately twice as much in metal value.

Purity is verified through acid testing or electronic testing equipment. Hallmarks — the small stamps inside rings or on clasps — indicate the declared purity, but a professional always verifies rather than relies on markings alone.

Weight

Once purity is established, weight determines the metal value. Gold jewellery is weighed on precision scales to the nearest hundredth of a gram. The calculation from there is straightforward: weight of pure gold multiplied by the current spot price per gram.

Condition and Craftmanship

For most gold jewellery, condition affects value only if damage is severe enough to reduce the recoverable metal. A bent chain, a broken clasp, or surface scratches do not diminish the metal value. However, pieces with significant solder repairs, mixed metals, or structural damage that affects weight accuracy will be noted.

For certain gold items — antique pieces, signed designer pieces, or items with historical significance — craftsmanship can add value beyond the metal. A Georg Jensen bracelet or a Georgian mourning ring may be worth more intact than as metal alone. This is assessed case by case.

What This Means for You

If you are selling gold jewellery, the most important variables are the purity and the current spot price — both of which are entirely transparent. At Miller Hirsch, the spot price used in the calculation is shown to you, and the purity is verified in front of you. You can follow the arithmetic from start to finish.

Diamonds

Diamonds are assessed differently from gold because their value is not anchored to a single global price index. Diamond pricing is driven by a more complex set of factors, and the secondary market operates quite differently from the gold market.

The 4Cs — and Their Limits

Cut, colour, clarity, and carat weight are the foundation of diamond grading. They describe what a stone is with precision and consistency, and they appear on grading certificates from laboratories such as the GIA (Gemological Institute of America). But as we explored in our detailed guide to diamond value, the 4Cs are a grading system, not a price guide. Two diamonds with identical 4C grades can trade at very different prices depending on factors the certificate doesn't capture.

What a Buy Appraisal Adds

When assessing a diamond for purchase, a buy appraisal goes beyond the certificate to consider:

• Current wholesale market pricing for the specific combination of cut, colour, clarity, and carat weight — which fluctuates and is tracked by professional buyers in real time

• The grading laboratory — a GIA certificate carries significantly more weight in the wholesale market than a certificate from a less rigorous grading body

• Cut style and current demand — round brilliant diamonds are the most liquid shape; fancy shapes move in and out of fashion, and their market value reflects current buyer appetite

• Fluorescence — strong blue fluorescence attracts a discount in the wholesale market for most buyers, regardless of how the stone looks to the naked eye

• The impact of lab-grown diamonds — the availability of high-quality lab-grown stones at lower prices has affected the secondary market for natural diamonds, particularly in smaller sizes; a current buy appraisal accounts for this reality

• Liquidity — how readily the specific stone can be resold at wholesale affects what a buyer can offer for it

Stones Without Certificates

Many diamonds — particularly older pieces, inherited rings, and stones originally purchased before GIA certification became standard — have no certificate. An experienced buyer can assess these stones directly under magnification, estimate their grades, and apply current market pricing accordingly. The assessment may be less precise without independent grading, but it can still produce a fair and well-reasoned figure.

Coloured Gemstones

Coloured gemstones — sapphires, rubies, emeralds, alexandrites, spinels, and others — are the most complex category of all, and the one where the depth of the assessor's expertise matters most.

Unlike gold, there is no spot price. Unlike diamonds, there is no single globally standardised grading system. Coloured stone valuation is part science, part connoisseurship, and heavily dependent on current market dynamics that shift with collector trends, major auction results, and geographic supply changes.

Colour

Colour is the primary driver of value in coloured gemstones, and it is assessed across three dimensions: hue (the basic colour), tone (how light or dark it is), and saturation (how vivid or muted). A vivid, well-saturated blue sapphire commands a dramatic premium over a pale or overly dark stone of the same weight.

The most prized colours have specific names in the trade — "cornflower blue" for sapphires, "pigeon's blood" for rubies — and these descriptors carry real financial weight among serious collectors and buyers.

Origin

Geographic origin has an outsized effect on the value of certain coloured stones. Kashmir sapphires, Burmese rubies, and Colombian emeralds command significant premiums over stones of equivalent appearance from other origins — premiums that can only be confirmed by laboratory testing. Origin certificates from respected laboratories such as Gübelin or SSEF add substantial value to significant stones.

Not every stone can be identified by origin without testing, and not every stone warrants the cost of origin testing. An experienced assessor can identify the likelihood of certain origins and advise accordingly.

Treatment Status

The vast majority of commercial coloured gemstones are treated — most commonly by heat, which enhances colour and clarity. Heat treatment is widely accepted and does not dramatically reduce value for most stones. However, untreated stones of significant quality command meaningful premiums over treated equivalents, because they are rarer.

Other treatments — fracture filling, beryllium diffusion, lead glass filling — are more significant and can substantially affect value. A buy appraisal assesses treatment status carefully, because an undisclosed treatment can turn a seemingly valuable stone into a considerably less valuable one.

What This Means for You

If you have coloured gemstones to sell — whether loose stones, set pieces, or inherited jewellery — the quality of the assessment you receive is entirely dependent on the experience of the person conducting it. Coloured stones cannot be assessed accurately from a photograph, a weight, or a basic description. They require hands-on examination by someone with years of exposure to the market, the stones, and the variables that drive value.

This is precisely why a buy appraisal from Miller Hirsch — conducted by valuers with more than 55 combined years across every level of the diamond and gemstone industry — provides a level of accuracy and transparency that a generalist assessment cannot.

Whatever you have — a gold chain, a diamond ring, a sapphire brooch, or a box of assorted pieces from a deceased estate — a buy appraisal gives you honest, expert answers about what each item is worth today.

Book your free buy appraisal with Miller Hirsch today — no obligation, no pressure, and a written explanation of every figure.