Kimherley Diamo7ids : Especially Cleavage Diamonds. 75- 
arranged anyhow in rounded lumps. The prevailing colour is grey, and in 
the mass it is opaque. But very elegant cubes and spheres of this material, 
ranging in colour from fawn to dove, occur which are quite translucent. 
Typical Wesselton bort is a sort of semi-translucent substance, black by 
reflected light, with a lustre remotely reminiscent of tourmaline. We meet 
with occasional fragments of black bort, an amorphous material perhaps 
more nearly allied to carbonado than to true diamond. This occurs in 
greater abundance in the Transvaal workings than at Kimberley, and pieces 
have been found on the Yaal River and at Jagersfontein. It occurs in the 
form of irregular lumps, and is not favourably regarded as diamond at all 
in the market. A beautiful and unique specimen of this class, in shape 
generally rounded but with the corners sticking out, much like a De Beers' 
yellow stone in habit, is in my keeping. D. P. McDonald has described a 
piece of this kind of bort in " Notes on a Form of Black Diamond from the 
Premier Mine" ('Trans. Greol. Soc. S. A.,' 1918). This material is now 
known as framesite. 
Bauer's statement that 90 per cent, of South African bort comes from 
the Kimberley Mine was wrong when he wrote it, and is still more wide of 
the mark now. 
7. Stewartite. 
The most interesting and most important individual of all the very 
diverse bort family is the substance for which the name " stewartite " has 
been adopted, and which claims a section for itself. This was discovered 
by J. Stewart. It is of a steel-grey colour, with a dull steely sheen, and is 
more fibrous in texture than the types of bort mentioned above. In hardness 
it equals the diamond, but its specific gravity is rather less.'-' It is a good 
conductor of electricity, like other borts. Its most remarkable property, 
though, is that it is magnetic and polar, and thus it has an important bear- 
ing on Crookes's theory that diamond has separated out from molten iron. 
Being magnetic, it must contain iron ; and because it contains iron and 
carbon in association and is polar, we might almost call it a steel bort. 
Hitherto iron had only been found in infinitesimal quantities in the ash left 
after burning a diamond. 
The properties of stewartite recall those of the fabulous, or alchemical, 
adamant of the Middle Ages, when a confusion of ideas (for it is difficult 
to conceive that there could have been an adequate knowledge of the facts) 
seems to have evolved an imaginary substance combining the properties 
of diamond and lodestone. Chaucer seems to have distinguished between 
diamonds and lodestones, though possibly not by intention, using the 
spelling " adamauntes " for the latter and " ademauntz " for the former. 
Thus (Morris's ed., 1886) : 
* S.G.=3-45. 
