. The geology of the goldfields of British Guiana. f the jNIahdia, and in some of the higher ravines, great blocksof diabase are of conunon occurrence in the gravels. Ihe overburden in the placeis in the Minnehaha District \ariesgreatly in deptli. Near the junction of the Minnehaha Creek, withthe Konawaruk, the stripping is very deep, but as the creek head isapproached the depth of the overburden decreases, until at its sourcethere is none. In some of the tributary streams, near the head of theMiniiehaha, the overburden is deep, and contains great blocks of^liabase, whilst the gra^els largely
. The geology of the goldfields of British Guiana. f the jNIahdia, and in some of the higher ravines, great blocksof diabase are of conunon occurrence in the gravels. Ihe overburden in the placeis in the Minnehaha District \ariesgreatly in deptli. Near the junction of the Minnehaha Creek, withthe Konawaruk, the stripping is very deep, but as the creek head isapproached the depth of the overburden decreases, until at its sourcethere is none. In some of the tributary streams, near the head of theMiniiehaha, the overburden is deep, and contains great blocks of^liabase, whilst the gra^els largely consist of partially decom])osedangular fragments of that rock. Owing to the great depth of the stripping in the lower coui-se of thecreek the gravels have not been worked t(» any extent. AVhere theyhave been worked the avei-age dej»th of stripjung is about fi\e feet, andit consists of a reddish-brown to yellow earthy clay. Tlie gold-bearinggravel consists of fine nuaitz frairments, with blocks <if more or less Platv; 30. To face. pngp. if -•^F— ^? PLAC ER WORKl N G. SLUICE AND TAILINGS. PhAo by II. I. Fcrkiiis Tlie Iloxer Deposits. i03 altered ([uartz-porphyiy and small pieces of sandstone. Towards thehigher parts of the valley the gravel is coarser, and consists of roughangular ijuartz shingle, and fi-agnients of partially decomposed diabaseand quartz-pori^hyry. The average depth of the gravel is about threeand a half feet, and its yield of gold is aljout two jjennyweights to thecubic yard. In this district the gold is always very fine. The placer gra%els on the Konawaruk River are somewhat shallow,the average depth oi their cnerburden being about two feet. Thisconsists of yellowish cla}^, and is underlain by about three and a halffeet of greyish-brown, very angular quartz gravel. The gravel yieldson the average about one and a half pennyweights of somewhat coarsegt)ld per cubic yard of the pay-dirt. The foregoing brief descriptions of some of the mijre importa
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectgeology, booksubjectp
