In the opening decades of the 19th century supplies began to be drawn from Banka; in 1820 this island contributed 1200 tons; the production was increased to 12,000 tons in 1900, when a diminution set in, 9960 tons being the output during 1905.
The world's supply in 1900 was 72,911 long tons; this increased in 1904 to 97,790 tons, but in 1905, principally owing to a shortage in the supplies from the Straits and Banka, the yield fell to 94,089 tons.
Of the several commercial varieties Banka tin is the purest; it is indeed almost chemically pure.
Diamonds are obtained in Borneo, garnets in Sumatra, Bachian and Timor, and topazes in Bachian, antimony in Borneo and the Philippines; lead in Sumatra, Borneo and the Philippines; copper and malachite in the Philippines, Timor, Borneo and Sumatra; and, most important of all, tin in Banka, Billiton and Singkep. Iron is pretty frequent in various forms. Gold is not uncommon in the older ranges of Sumatra, Banka, Celebes, Bachian, Timor and Borneo.
The islands are often described as of two groups, Java and Madura forming one, and the other consisting of Sumatra, Borneo, Riouw-Lingga Archipelago, Banka, Billiton, Celebes, Molucca Archipelago, the small Sunda Islands, and a part of New Guinea-the Outposts as they are collectively named.