546 Prof. Tennant — South African Diamonds. 



South Africa, and said that if people only knew them in the natural 

 state he felt confident they would be found. 1 He died in 1829, and 

 I took every opportunity to make the subject known by means of 

 short papers, accompanied by figures showing the ordinary crystal- 

 line form of the diamond. 



The number and quality of diamonds from the Cape are equal to 

 those from the Brazils, which have chiefly supplied Europe during 

 the last eighty years. 



Ahout ten per cent, of the Cape diamonds may be classified as 

 of the first quality, fifteen per cent, of the second, twenty per cent, 

 of the third ; the remainder, under the name of bort, are employed 

 for cutting diamonds, and for the various economic purposes to which 

 this valuable substance is applied by the glazier, the engineer for 

 drilling rocks, the lapidary, and others. Many diamonds contain 

 specs and cavities ; these are placed in the hands of skilled workmen 

 who are acquainted with the cleavage, and by careful manipulation 

 they are frequently able to remove these blemishes, and so to obtain 

 portions of the gems of the first quality for making small "bril- 

 liants," " roses," and " tables." 



The cutting and polishing of diamonds was carried on in London 

 with great success 200 years ago ; subsequently it was carried on 

 chiefly in Holland ; but several attempts have been made to re-estab- 

 lish the trade in this country. 



In 1874 the Turners' Company offered prizes, in the form of 

 medals and the freedom of the City of London, for the best specimens 

 of diamond-cutting. The Baroness Burdett-Coutts has supplemented 

 this by the addition of money prizes, and has offered to contribute 

 the further sum of £50 for prizes in the year 1876. 



It is estimated that the value of the diamonds found at the Cape 

 from March, 1867, to the present time, exceeds twelve millions 

 of pounds sterling. 



I am enabled to exhibit not only a large collection of these 

 diamonds, but also samples of the natural materials found associated 

 with them. 2 In November, 1873, one of my former students brought 

 me the specimen from South Africa represented in Fig. 1, which in 

 its original state weighed 112 carats; it has since been cut by a 

 London firm of diamond-cutters into the beautiful brilliant repre- 

 sented by Figs 2, 3, and 4, weighing 66 carats. The stone has a 

 delicate yellow tinge, and exceeds in size and brilliancy any diamond 

 in the British Crown. 



It may be remarked, with regard to this class of gem-cutting, 

 that 200 years since the English diamond-cutters were the most 

 celebrated in the world. The diamond-cutting trade is now 

 coming back to England, and the stone figured above affords a fair 

 sample of what excellent work can now be done here. I may 

 mention that the stone in its present form is worth £10,000, 



1 Prof. Tennant explained that the diamond in its natural state bore considerable 

 resemblance to a piece of gum. 



2 Prof. Tennant exhibited a South African diamond in the matrix (consisting 

 chiefly of broken fragments of «hloritie and clay-slates) , likewise some interesting 

 photographs of the Diamond-workings in South Africa. 



