able quantities and some in traces; and in addition platinum molybdenum, petroleum, catseyes, and spinelle ruby have been observed. In Sir J. Brooke's "Private Letters" mention is made of a large stone called the "Brooke diamond" which on examination proved to be a white topaz, but the precise locality whence it was obtained is not specified, although we may surmise that it was a genuine Sarawak stone.
I find also in a work on China entitled "The Middle Kingdom" (1848) mention of Corundum being imported from Borneo for the use of Chinese lapidaries; no authority, however, is cited for the occurrence of this mineral in Borneo: the note probably refers not to Corundum, properly so called, but to diamonds, brought from Landak and Sarawak.
In the above enumeration it is noteworthy that Sarawak Proper exhibits all the minerals of which traces have been detected in the other districts, and several others besides. When we consider that it is the only portion of the Territory in which a systematic search has been attempted (generally by amateurs) and that there is a close general similarity in geological constitution over the whole of the N. W. coast of Borneo, there is fair ground for conjecture that available deposits of one or more of the above mentioned minerals, will be discovered in some other localities in which traces only have been detected as yet.
Gold occurs in the form of fine sand, or minute flattened plates in alluvial deposits over a great part of Sarawak. Washings are carried on in Upper Sarawak at Bau, Paku, Gumbang, &c., in Samarahan at Sirin, in Sadong at Malikin, and in the Batang Lupar at Marup. The operations are wholly superficial, although at Marup and Bau, the principal Chinese washings in the country, the stratified clays belonging to the Sandstone formation, and containing at the latter locality decomposed porphyritic dykes have been cut into to some extent. The precious metal has never to my knowledge been regularly mined for in Sarawak, nor indeed has it been discovered in situ it its original matrix, except in the case of the gold contained in the veinstones and quartz-reefs of the Antimony district, and that associated with a lode of argentiferous arsenic at Bidi. The alluvium of the limestone caverns and fissures, and especially the sands in the beds of streams have yielded sufficient to induce the natives to work in such spots. The washing is carried on partly by Malays, who are usually gamblers and work only at intervals, but chiefly by country-born Sambas Chinese. Their mode of operation has been fully described by Crawfurd, Horsfield, St. John, and others, and it will therefore be unnecessary to enter into any details here.
