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diamond; transparent yellow-white octahedral crystal, with minor development of trisoctahedron and hexoctahedron; shows minor alluvial damage, and greenish radiation spots

[Golconda, Hyderabad, Andhra Pradesh], [India] unknown Very fine. Found un-numbered in gem collection, and with no label, but almost certainly from William Hunter's collection, as the only recorded large diamond in our collections. The Fordyce catalogue of 1794 gives on P 105 "A complete crystal of a Diamond, from Golconda. It is colourless". Robert Jameson's catalogue of 1810 describes under No 1. "..In the first box, two crystals of diamonds in the largest crystal each [?] is divided into six so that the figure has 48 sides". This fits with the observed minor crystal faces. The chemist Thomas Thomson weighed "the very fine transparent diamond in the Hunterian Museum" in 1836, using an improved balance, and got a weight of 10.825 grains. He converted this to 3.518 carats, which in 1836 corresponded to a value of £24 15s. On a modern gem balance the stone weighs 3.50 metric carats: there can be no doubt that this is the same stone.

Two edges show minor damage typical of alluvial diamonds, and there are several small, near-surface greenish spots caused by proximity to radioactive minerals - these are again common in alluvial diamonds.

It is interesting that the weight of this stone in carats 3.50 is almost exactly the same as the density of diamond: 3.51 g per cc.