Page:Journal of the Straits Branch of the Royal Asiatic Society (IA journalofstrait121878roya).pdf/54

26 The most considerable quantity of ore has been gained, not by vein-mining, but by washing in the felspathic clays flanking the western aspect of the hill. These clays afforded pure stream Cinnabar in great abundance, as well as hundreds of rich boulders of ore-bearing rock that had been denuded from the upper parts of the hill. This source of wealth, however, was limited, and may be regarded as exhausted.

A search for fresh deposits has been instituted from time to time. Traces of Cinnabar have been detected behind the Sibugoh mountain and in the Samaraham and Sadong districts; and traces of metallic mercury have been reported on good authority at Marup in the Batang Lupar; and at Gunong Gading, a few miles to the west of Tagora, ore has been discovered in situ, and is being worked. The Gading deposits are altogether smaller and much poorer than those at Tagora. The general geological features of the two hills are similar, but the matrix at Gading is more siliceous and more highly metamorphosed, though at the same time decomposing rapidly on exposure to atmospheric influences, as is also the case with the Tagora rock. The character of the Cinnabar differs from that of the Tagora deposits, being soft and crystalline, and the ore in the stream-washing is small and very friable, and so abundantly mixed with iron-pyrites as to make it impossible to separate the two minerals by simple hand-washing.

As with the antimony there is evidence of the association of minute quantities of quicksilver, so too, antimony (sulphide) has been observed in juxtaposition with the Cinnabar in the same fragment of veinstone at Gading.

With regard to the origin of these deposits of Cinnabar, it is almost certain that they were produced by the passage of heated vapours bearing quicksilver and sulphur in a state of sublimation, which were deposited by the cooling of the vapours as they approached the surface of the earth. The peculiar and irregular mode of deposition of the Cinnabar, and the facts that the lower the miner goes the less abundant the ore becomes, and that no definite "run," or fissure vein, is observable, all point in this direction. It is confirmatory of this view, that the surrounding shales and sandstones are all more or less highly impregnated with peroxide of iron, whilst in the metamorphic ore-bearing rock, iron is scarcely visible except in the form of pyrites, i.e. in combination with sulphur, which can only have risen from below in a state of sublimation, and has seized on the iron and collected it in this form. Assuming a large proportion of sulphur in the