Notes on the Society's Work in 1891-1918. lxxv. 



The problem of the origin, concentration and distribution of the 

 Guiana auriferous deposits is too complex to be dealt with in this address 

 which has already far exceeded its prescribed limits. In 1897 this problem, 

 if it had then been ripe for discussion, might have been dealt with at the 

 Institute of Mines and Forests, but as that organisation no longer exists, 

 except as a recruiting and registering agency for labourers for the interior, a 

 paper on the question followed by a discussion would not be out of place 

 in this room at some later date. 



Diamonds. 

 Diamonds were first found in quantities in 1890 by Mr. 

 Gilkes whilst working as a prospector for the late R. F. Kaufmann, — 41 

 diamonds weighing 13 carats being brought to me for mineralogical exami- 

 nation on July 30th, and 518 weighing 198 carats being being similarly sub- 

 mitted by Mr. Kaufmann on November 24th of that year but — little interest 

 appears to have been taken in the occurrence of these gems in the colony 

 by this Society. Although from 1890 to 1899 diamonds were found in 

 many districts of the colony, usually singly or a very few in any one place, 

 little was done towards the systematic working of the deposits until Mr. 

 Gilkes, about 1899, succeeded in interesting persons outside the 

 colony in their occurrence here. From that time the exploitation of 

 diamonds has been one of the recognised industries of the colony. In 

 round figures 136,400 carats of diamonds representing probably consid- 

 erably more than a million crystals, have been won in the 

 colony and exported since 1900. For that year the export of 

 diamonds was returned at 996 carats. In 1902 to 1904 the average 

 yearly export of diamonds was 10,720 carats. The output fell during 

 the next three years, only 1,860 carats having been exported in 1907 ; 

 it again slowly increased, the average annual export during the period 

 1911 to 1914 being 7,750 carats ; whilst during the two years 1916 and 

 1917 the mean annual export increased to 16,580 carats. These recent 

 records are encouraging and the exploitation of the colony's diamant- 

 iferous deposits promises to take an important part amongst its 

 industries. 



Iron-ores. 

 There are vast surficial deposits of lateritic iron-ore in the colony, 

 the ore invariably being characterised by its extremely low content of 

 phosphorus and usually by a low content of sulphur. The utilisation of 

 these wide-spread deposits is a problem of the futnre which I fear will 

 have to await the economic development of the vast water-power poten- 

 tialities of the cataracts on our rivers. There are also indications of 

 rnagmatic deposits of specular iron-ore of a very high quality in the 

 North Western section of the colony. Should any one of these latter de- 

 posits be proved to be of sufficient area it may soon become of export value. 



Bauxite. 

 Closely allied in origin to the lateritic iron-ore is the bauxite of the 

 colony. The specimens which led to the discovery of the wide-spread 



