Dr. F. B. Hatch— Gem-Qravel, W. Coast of Africa. 107 



fixed intervals across the alluvial flats. The pits were then sunk, the 

 overburden being discarded and the gravel washed. _ _ Concentration 

 was effected by the ordinary methods of sluicing and sizing by sieving, 

 the final product being obtained by hand-jigging. Froni this the 

 diamonds were recovered by hand-picking. The following is the 

 number and weight of diamonds found during the prospecting 

 operations carried on during 1910 and during the first part of 1911 : 

 247 stones, weighing 85|^ carats, in the Jiblong River, and 22 stones, 

 weighing 4if- carats, on the Bor Eiver. The largest stone found 

 weighed 4|-f carats. Diamonds were found in the Jiblong River and 

 in its alluvial flats for a distance measured along the river of a little 

 over a mile and a half. This stretch of the river is situated between 

 the rapids below the Pakla Ta Falls and the small falls above the 

 Yema Ta Falls (see Map). This stretch of country is comparatively 

 flat, but measured ^ from the top of the Pakla Ta JFalls to the bottom 

 of the Yema Ta Falls the river has a total drop of ahout 100 feet. 



Sketch-map of the Jiblong and Bor Elvers from a survey by S. M. Owen. 

 Scale, 1 inch = l mile. The area in which diamonds have been found is 

 indicated by a pecked line. 



The average width of the flats in which the diamonds were found is 

 238 feet. The average thickness of the diamantiferous gravel between 

 the overburden and the bed-rock was found to be 6 feet. Diamonds 

 were also found in the Bor River which joins the Jiblong at Careysburg, 

 three miles below the Yema Ta Falls, but no extensive deposit exists 

 in this river valley. 



The samples of the ' deposit ' or concentrate from which the 

 diamonds had been picked, consisted of a mixture of heavy minerals, 

 together with quartz, limonite, and rock fragments. The quartz was 

 ^ According to a survey of Mr. S. M. Owen, A.E.S.M. 



