104 Transactions of the Royal Society of South Africa. 
colour imparted to coated stones by indefinitely thin layers of tiny black 
spots), and is the happier as the laminae are thinner. Thus the colouring 
matter is an overgrowth which establishes the lamination. There is no 
doubt that Heddle when he alleged the disseveration of " plate diamonds " 
('Ency. Brit.,' 9th Ed., Art. Mineralogy "), was confounding the mythical 
bursting of smoky stones with the lamination of brown ones. 
[Addendum. — While the above paper was going through the press I had 
the good fortune to see a most important specimen of diamond embedded in 
calcite, found by Mr. J. T. Vigne in the working over of some old Kimberley 
lumps. The diamond appears to be of about four carats, and the enclosing 
calcite perhaps five carats. The diamond has evidently not been squeezed 
into the calcite, but has acted as a nucleus upon which the latter has 
crystallised. Mr. J. Stewart has, also, given me a portion of a beautiful 
shell of calcite taken from a Wesselton blue-ground diamond. The interior 
faces of this shell have acquired, from their intimate contact with the 
diamond, an almost perfect adamantine lustre.] 
