74 
Trmimctions of the Royal Society of South Africa. 
The lighter greens are nearly always found among rounded octahedra, and 
the colour appears to be concentrated in the crystal corners, and hence 
almost entirely disappears in the cutting, as we are told and should half 
expect. The sage greens are disappointin^'• as brilliants ; though they are 
uncommon they are not prized, for they have no life and little beauty. 
Steel blue and sapphire blue diamonds, like those from the Premier Mine in 
the Transvaal, have not been found near Kimberley. 
Brown diamonds ranging in colour from smoke-brown to chocolate are 
found, those of the latter colour rare and precious as brilliants when they 
possess "fire." Beautiful pale brown and autumn brown stones, of large 
size up to a hundred carats but of flat and irregular habit, used to be found 
in the Pool. Inexperienced diggers have been known to throw them away, 
mistaking them for "Dutch bort " (zircon). One fine piece, worth upwards 
of d£200, was ascertained to have been thrown away by one debris washer 
after another before it finally reached the market.. Such stones cut very 
well. Their early history in the pipes must have differed much from that 
of the majority of diamonds. 
After all, if the truth must be told, the common yellow diamond is 
by far the most beautiful of all, and it would be esteemed the most if it 
were less common. And it has this advantage, which a good many white 
stones have not — that it is full of fire by day or by night. The great Tiifany 
lemon yellow brilliant is a proof of this affirmation. Judging by descriptions 
and by glass copies, it is a Dutoitspan diamond.* 
Stones shownig slight colour effects under the polariscope are not at all 
uncommon, but they are conceivably not so common as is sometimes asserted. 
The statement that nearly all Kimberley diamonds show signs of great 
internal strain is no more than assumption based on casual examination of a 
comparatively few specimens, and is scarcely more likely to be generally true 
than the old idea, still believed by many — that all diamonds phosphoresce 
after exposure to sunlight. How ma,ny South African diamonds ever go 
near a polariscope ?t (But see Sir William Crookes's Kimberley lecture on 
Diamonds, 1905.) 
6. Bort. 
Perhaps the bort class is the most interesting of all. " Bort " as a com- 
mercial term includes inferior representatives of all the other classes besides 
true bort. True bort consists of crystalline aggregates of tiny particles 
* The Tiffany diamond is commonly said to have been found in the Kimberley 
mine in 1878. The diamond fields newspapers of that year, however, do not report 
such a find. 
t Crystals and crystallisation have always provoked random theories. Note, e.g. 
the old and utterly unobservant idea, endorsed by no less a philosophic autocrat than 
the ' Encyclopaedia Britannica ' that " hoar frost is nothing but dew turned into ice 
by the coldness of the air" (3rd edition, 1797). 
