Page:Journal of the Straits Branch of the Royal Asiatic Society (IA journalofstrait121878roya).pdf/45

Rh Nuggets are of extremely rare occurrence and I have never seen one of any size, but if the Chinese are to be credited, some of very considerable weight have been met with in the adjacent Sambas District. St. John mentions having seen one of 7 oz., taken from the auriferous clay at Krian near Bau, and this is the largest which I have heard reported on credible authority to have been found in Sarawak. The gold dust is usually in a state of the finest comminution, but I have seen samples from Kumpang, near Marup, composed of fine dust intermixed abundantly with thin flat plates of the metal of from to  inch diameter—a form which has been ascribed to some original laminated structure in the present matrix. I am informed that similar plates have been detected in the siliceous veinstones of the antimony lodes; but where I have had the opportunity of seeing the gold in these veinstones it appeared in very minute sparsely scattered specks without a sign of running into plates or veins. The veinstones are now and again found to contain a very profitable percentage, according to the estimate of the Chinese, who quarry the stone in a superficial way, and pounds it in wooden mortars with iron rammers. One block of siliccous matrix (about 15lbs.) at Paku containing some 20 per cent of grey antimony, when thus crushed yielded about $12 worth of gold, but this result was quite exceptional. At Jibong both the white quartz and the black amorphous siliceons veinstones are crushed, and of these two the latter is considered to yield the higher percentage of metal. Both in crushing the stone and in washing the alluvial clays and gravels the find is very uncertain, and good "hauls" seem few and far between. Marup, Bau, and Paku have afforded remunerative washings, and Sirin in a less degree. The succession of the superficial deposits in the last locality are as follows:—


 * 1) Vegetable mould.
 * 2) Unstratified Felspathic clay.
 * 3) Clayey Gravel.
 * 4) Uptilted indurated clay-shales.

The whole section to the basement-rock of clay is only 5 or 6 feet in thickness, and it is in the stratum of gravel that the gold is found, associated with small rolled fragments of cinnabar and the clay-ironstone which abounds all over the gold and antimony districts of Sarawak. The components of the auriferous gravel are granite, quartz, sandstone, impure-agate, porphyrite, &c. The surrounding country is made up of steep low hills of indurated clay-shales and clayey sandstone with yellow felspathic clay overlying, and is scamed with dykes of hornblendic trap-rocks; and a short distance to the S. and W. limestone hills appear.