Original plaster cast of the Koh-i-Noor, replica in cubic zirconia, the modern form of the cast A.Hart Original plaster cast of the Koh-i-Noor, replica in cubic zirconia, the modern form of the cast

75 Years of Swiss Gemmological Expertise: Alan Hart at The European Gemmological Symposium 2017

Gem-A CEO, Alan Hart, attended the European Gemmological Symposium last week in Zermatt, Switzerland where he presented an exclusive talk highlighting the case of the Koh-i-Noor. The Symposium, consisting of two days of Conference, coincided with the prestigious 75th Anniversary celebration of the Swiss Gemmological Society (SGS).

Across the two days there was an impressive selection of 24 internationally distinguished speakers from across the industry, delivering an extensive collection of gemmological focused topics from diamonds and pearls to coloured gemstones and jewellery.

Read more: Line-up of symposium speakers

Alan Hart explored the case of the Koh-i-Noor; questioning whether the differential hardness of diamond is directly responsible for the form of Mogul cut stones. Within his talk, Alan focused upon the historical origins of arguably one of the world's most famous diamonds, drawing the interest of many conference attendees.

Originally referred to as 'Mountain of Light' in Persian, the flat 105.602 carat oval stone now sits at the centrepiece of the Queen Mother's Coronation Crown. Despite the stone culminating as an end product of an original historical 'Mogul cut' diamond and thus criticised for its lack of fire and brilliance in the Great exhibition of 1851, today, close to three million visitors gather to see the British Crown Jewels at the Tower of London.

Early origins of the Koh-i-Noor are limited and contradictory in nature which is why, even today, there remain a number of issues questioning when and who cut this beautiful historical stone. A unique plaster cast replica of the original stone, commissioned by the British Museum in 1851, was re-discovered amongst the Mineral Collection of the Natural History Museum. Alan showcased how through analytical techniques from simple modelling to laser x-ray scanning, a unique cubic zirconia replica was used in a comprehensive 'crystallographic study' to elucidate the nature of the style of the 'Mogul cut'.

We know from rare and brief historical descriptions that skilled Indian lapidaries were aware of identifying the 'grain' within a diamond. Stereographic projection, identifying cleavage planes on the original form were used to re-orient the diamond within the cubic framework as well as superposition of differential hardness variations of diamond. This itself reveals that alongside the supposed original rough morphology, use of primitive techniques and wear rates, directional hardness anisotropy was the major physical constraint leading to 'Mogul cuts' final form.

Read more: The Koh-i-Noor Diamond at The Tower of London

We can infer that other Mogul and 'Mogul style' stones of this period, such as the Taj-e-Mah and Orlov were cut in similar ways with similar constraints. Any Mogul style form that does not align to this cubic framework therefore results from directional hardness anisotropy and cannot be considered genuine.

This research provides thought-provoking discussion on how the original Koh-i-Noor may have been cut and by whom as well as its complexity in being considered a unique artefact of its time. Such research further questions whether the intricacies of its properties are the result of a combination of European and Indian cutting styles. It is clear however, that the re-cutting of Koh-i-Noor in 1851 led to over 400 years of its history lost forevermore. Whilst an assuming 160 year old plaster cast of a diamond may initially appear uninteresting, this research demonstrates how collections can be unlocked and utilised in many fascinating and diverse ways.

For further event information please visit Gemmologie.

Interested in finding out more about gemmology? Sign-up to one of Gem-A's courses or workshops.

Cover image: Original plaster cast of the Koh-i-Noor. Image courtesy of A.Hart


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