Buying A Diamond At Auction

With an eclectic range of contemporary, vintage and antique pieces available, jewellery auctions are an excellent place to consider when looking to source a diamond. As with any major purchase or investment, doing some informed research and becoming familiar with the market is highly recommended. Read on to discover how to get started, with key points to consider and questions to ask, no matter your taste or budget.

To begin with, let us look at the basics of diamond grading. Diamond quality is determined by a system colloquially known as ‘The Four Cs’, referring to cut, colour, clarity and carat weight. Together these four factors form the basis of a classification system for diamond grading that influences values.

A three stone diamond ring, featuring a central emerald cut diamond weighing 1.96cts, flanked by further emerald cut diamonds totalling 0.95cts, in platinum. Sold for $17,360

The cut of a diamond refers to its shape and proportions. Stones may be cut in a variety of shapes including round brilliant, baguette, emerald, square, pear, cushion and marquise to name only a few. Whilst choosing a cut is predominantly personal preference, ensuring the stone has good proportions is important. The proportions of a stone are the specific facet lengths and angles, all of which can affect the brilliance of the stone.

Naturally occurring in a full range of colours including pink, yellow, blue, green, grey and even black, diamonds are commonly graded on a scale of colourlessness. Starting with D and running down the alphabet, diamonds are graded from colourless through to white and tinted. Much like the cut of a diamond, colour can often come down to personal preference although colourless and near colourless diamonds command a higher price. In the case of rare ‘fancy coloured’ diamonds such as a natural vivid blue, scarcity drives the value upwards. Only 1 in 100,000 qualifies as a natural fancy coloured diamond!

Clarity is the third important element that categorises the stone purity. Evaluating the clarity of a diamond involves assessing the naturally occurring internal characteristics, noting the shape, colour, size, and positioning within the stone. The GIA (Gemmological Institute of America) has formulated a grading scale to describe these characteristics running from Internally Flawless through to Included. Whilst some inclusions may be visible to the naked eye, many are only visible with a 10x loupe. Keep in mind that these natural inclusions are what makes each diamond unique!

A solitaire diamond ring, the old European cut diamond weighing an estimated 4.05cts, in a decorative coronet setting, in platinum. Sold for $44,640

The final component is the diamond carat. Diamonds are measured by weight rather than size, and therefore the heavier the diamond the greater the carat weight. Pricing is determined by an exponential scale since the larger carat weights are generally rarer and more desirable, making them higher in value.

Once familiar with the basics of diamond grading, there are some specific points to consider before bidding on a diamond at auction. A jewellery specialist can help with these technical questions:

Does this diamond have fluorescence?
Fluorescence refers to a diamond’s tendency to emit a soft glow when exposed to ultraviolet light. Many diamonds have some degree of fluorescence. Under certain light conditions, a slight fluorescence may make a tinted diamond appear whiter. In contrast, medium to strong fluorescence in a high colour stone may impact the brilliance of the stone.

Has the diamond undergone any treatment?
There are a host of treatments that can be applied to a diamond to enhance colour and clarity. Some treatments are stable and permanent, whilst some can compromise the structure of the stone, leading to potential damage during wear, repair or cleaning. It is important to understand what, if any, treatment has been applied, as this can significantly affect the value. Diamond treatments must be disclosed to buyers, and a jewellery specialist can further elaborate on any questions you may have about specific treatments and enhancements.

Is there any accompanying certification?
At auctions, diamonds are offered from a range of eras, some preceding certification. However, many modern diamonds are accompanied by independent laboratory reports. Whilst not essential, having certification is good for peace of mind and may be useful if reselling the piece in the future.   

What is the condition of the diamond?
Although incredibly hard-wearing, diamonds are still susceptible to some ‘wear and tear’. Often, abrasions and chips are only visible under loupe or microscope magnification, so request a condition report or ask a jewellery specialist to assist.

With several Important and Fine Jewels & Timepieces auctions per annum,  along with a weekly jewellery offering presented as The Jewellery Salon within The Thursday Auction, Leonard Joel has a truly eclectic offering of diamonds available.

Happy browsing!

BETHANY MCGOUGAN / Senior Jewellery Specialist

October 2020