Sworders Fine Art Auctioneers is about to auction the finest diamond the company has ever sold in its 200 year history.

The 3.41 carat stone is in a four claw platinum ring setting, and will go under the hammer at Sworders’ Silver & Jewellery Sale on Tuesday, May 20 in Stansted Mountfitchet, with an estimated selling price of £65,000 to £75,000.

Helen Jonas, from Sworders silver & jewellery department, said: “When it comes to evaluating the quality of diamonds, we work with what we call the ‘Four C’s’ - Carat, Cut, Clarity and Colour. This particular stone excels in every category and is accompanied by a GIA grading report – one of the most respected organisations in the diamond industry.

“To have a weight of nearly three and a half carats is exceptional; it’s one of the largest diamonds we have ever sold. In fact, it’s almost the size of the little fingernail of the model wearing it!”

The oval brilliant cut means that the diamond can refract light internally from one facet to another, before reflecting it back up through the centre to give the stone its characteristic sparkle.

Helen added: “Most diamonds contain tiny natural imperfections called inclusions, which interfere with the passage of light through the stone and affect their clarity; but this example is internally flawless.

“There is also no yellowish or brownish tint to the stone, meaning that it’s colourless – which is the best colour for a diamond to have! In short, we rarely see examples as fine as this one.”

Other highlights in the sale include some highly-collectable provincial Irish silver, a 1907 silver serving dish and cover by Guild of Handicraft with a guide price of £300 to £500, and a pair of natural pearl and diamond drop earrings which Sworders found loose in a large cardboard box amongst mixed costume jewellery, and surprised the owner with an estimated selling price of £3,000 to £5,000.

The sale starts at 10am. Entries are now being accepted for the next silver and jewellery sale on November 25.