96 Canadian Record of Science. 



that date.^ It may suffice to say that the diamond, first 

 discovered in 1867 in gravels on tlie Orange Eiver, was 

 found three years later in certain peculiar deposits, which 

 occur locally in a region where the dominant rock is 

 dark shale, sometimes interbedded with hard grits, or 

 associated with igneous rocks allied to basalt. These 

 deposits occupy areas irregularly circular in outline, and 

 bearing a general resemblance to volcanic 'necks. The 

 diamantiferous material, near the surface, is soft, yellowish 

 in color, and obviously much decomposed ; at a greater 

 depth it assumes a dull greenish to bluish tint, and 

 becomes harder. At the well-known De Beers Mine, near 

 Kimberley, the works in 1898 had been carried to a "depth 

 of about 1,500 feet, and the diamantiferous material, for 

 at least the last 100 yards, was not less hard than an 

 ordinary limestone. It has a brecciated aspect, the dark, 

 very minutely granular, matrix being composed mainly 

 of serpentine (about four-fifths of the whole), and of a 

 carbonate of lime (with some magnesia and a little iron). 

 In this matrix are embedded grains of the following 

 minerals : — -Olivine, enstatite, smaragdite, chrome-diopside 

 (omphacite of some authors), a brown mica, garnet (mostly 

 pyrope, but more than one variety observed), magnetite, 

 chromite, ilmenite, with several other minerals much 

 more sparsely distributed. 



Eock fragments are also present, variable in size, but 

 commonly not exceeding about an inch in diameter, as 

 well as in quantity. These occasionally, but not gene- 

 rally,^re rather abundant. In some cases tliey are chips 

 of the neighboring black shale, but in others they are 

 greyish-coloured with a somewhat porcelainised aspect. 

 The latter are generally sub-angular in form, and exter- 



1 Jules Gariiiei-, Geol. Sovtk Africa Trans., 1897, p. 91 ; H. S. Hurger, ihiJ., p. 124. 

 See also W. G. Atlier.stone, ibid.. ^S%, p, 76 ; L. De Lauiiay, Conipt. Read., 1897, cxxv., 

 33.0. The la.st auUioi', in " Les Uiamaiits ilu Cap " (fails, 1897) gives a very full acfount 

 of the mines, but an even better one will be found in Max Bauer, " Edelstelnkunde " 

 Leipzlc, 1896, p. 208). 



