. Discovery. Science. 268 South Africa is a gemmer. DISCOVERY Every native who owns a small plot He works at gemming during the dry season when he has little other work to do. and he looks upon gem-recovery as a pastime which is possibly remunerative. How did the Gems come There ? The geology of the gem districts of Ceylon is not of a complex'nature. The whole island may be taken to be of igneous origin. Granite and gneiss outcrop and protrude everjnvhere, showing evidence of some huge force that must once have piled the mass of rock to an enormous height, very much higher than the present sur
. Discovery. Science. 268 South Africa is a gemmer. DISCOVERY Every native who owns a small plot He works at gemming during the dry season when he has little other work to do. and he looks upon gem-recovery as a pastime which is possibly remunerative. How did the Gems come There ? The geology of the gem districts of Ceylon is not of a complex'nature. The whole island may be taken to be of igneous origin. Granite and gneiss outcrop and protrude everjnvhere, showing evidence of some huge force that must once have piled the mass of rock to an enormous height, very much higher than the present surface. The gems, no doubt, may have been in situ originally, but I have never seen or heard on the top or steep side of the hiUs—but a few are found in the beds of mountain streams and natural rock-riffles or depressions. The natural inference would be that the gems, being of greater specific gravity, would have remained more or less near the spot where they were released ; but I am inclined to think that, where a gem was encased in a piece of rock, it was carried away to the lower level, and there washed and rolled about imtil disintegration took place which released it. Those that were freed at the higher level became encased in the alumina-mud, or clay, or kaoline, which gave the mass sufficient buoyancy to be deposited in the lower gutters. These two processes would explain the fact that gems are seldom found at their spot of Fig. I.—cutting of a gem being found embedded in rock. The only instance which leads one to suppose that the gems were once in situ is that garnetiferous granite is found in quantities. On the cooling of the igneous mass, fissures and cracks and the lamination of the rock sur- face took place, and during the thousands of years of denudation and weathering, hundreds of feet in thick- ness must have been washed away to the lower vallej'S and into the huge fissures. The rock-debris became further decomposed and now forms the present surfa
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