Tin has been reported in placer deposits in the Winnebah district and in pegmatite dikes in the Mankofa and Mount Mankwadi districts of the Gold Coast. Tin has been found in placer concentrates from streams in Nyasaland. Tin deposits seemingly of little value have been found in the Enterprise district, east of Salisbury, and in the Ndanga district, east of Victoria, in Rhodesia. These deposits are stanniferous pegmatites which are found in schists near granite.
Australia.
—Tin is produced in the following provinces of Australia: Tasmania, Queensland, New South Wales, West Australia, Northern Territory, Victoria, named in the order of their importance. In 1907, the output of Tasmania was about 14,000 tons of concentrates, but production since then steadily declined until it became nearly stationary at 3,000 tons annually for the last few years, and it is believed that this output can be maintained for some time.
There are tin-smelting works at Launceston, in Tasmania; Woolwich, near Sydney, New South Wales; and Irvinebank, near Herberton, Queensland, capable of producing over 4,200 tons of metallic tin a year. Of recent years tin concentrate is being sent to the Straits Settlements (Singapore) for smelting. The exports of metallic tin from Australian ports in 1917 came to about 3,100 tons.
Practically all of the mining companies are controlled by Australian and English capital, and as the tin is smelted either locally or at Singapore the total Australian output can be considered as under the direct political and commercial control of England.
The total production of tin ore from Tasmania[143] from 1880 to 1918, inclusive, is stated to be approximately 128,200 tons.
[143] Tasmania, Report Secretary for Mines for the year ending December 31, 1918, p. 46.
The most important tin mine is Mount Bischoff, 45 miles southwest of Emu Bay. The deposits, discovered in 1871, are credited with a total production of about 75,000 tons of tin ore. There are several deposits, soft altered quartz porphyries intrusive into schists. Topaz and cassiterite are disseminated in the porphyries, and veins carrying tin and wolframite, together with pyrite and arsenopyrite, are found both in the porphyry and schists.
The Shepherd and Murphy mine, near Middlesex, is in a zone of metamorphism at the contact of granite, intrusive into sandstone and quartzite. Tin, tungsten, and bismuth are produced from this ore. Placer tin deposits on the Ringarooma River (Derby district) supply about 1,000 tons of tin concentrates a year. The principal placer mines are the Pioneer and Briseis. Near Gladstone, placers and lode deposits carrying tin and tungsten are worked. At the Anchor mine, in the Blue Tier district, a tin-bearing granite averaging one-half per cent. tin is worked, but mining has not been profitable. The Renison Bell, Dreadnought-Boulder and Montana mines, in the North Dundas field, are in slates cut by dikes of quartz porphyry. Zinc, lead, and iron sulphides are important in the lodes. In the Heemskirt district, southwestern Tasmania, the tin deposits are in granite and in overlying slate and sandstone. At the Federation mine the ore is in a pipe measuring 25 by 15 feet at the surface, but contracting to only 1 by 5 feet at 115 feet down.
Tin was first produced in Queensland in 1872, and the total output, including 1917, is estimated to be about 144,008 tons. The chief producing districts are Herberton, Cooktown, Chillagoe, near the port of Cairns; Stannhills, Kangaroo Hills, and Stanthorpe, the latter being near the New South Wales border. In the Herberton-Cooktown districts the tin occurs in greisenized granite intruded into slates, schists, and quartzite; bismuth and tungsten minerals are associated with it. Placer deposits are worked by hydraulicking, and in places the tin-bearing greisen is broken down by hydraulic giants. In the Stannhills field, near Croydon, cassiterite is found in veins in granite with galena, sphalerite, and chalcopyrite. The Kangaroo Hills, 100 miles south of Herberton, produces both lode and placer tin. In the Stanthorpe district most of the output is from placer deposits, some of which are buried under basalts.