The principal manganese deposits of Spain are on the south slope of Sierra Morena, in the Province of Huelva. Vertical lenticular bodies of manganese carbonate and silicate with a little pyrite, garnet, and mica occur interlayered with slate of Paleozoic age. About one hundred bodies are known, many being 500 feet long and 100 feet wide, whereas the largest is 3,300 feet long and 330 feet wide. The manganese minerals are weathered to oxides to an average depth of 65 feet and a maximum depth of 250 feet. From 1881 to 1905, when the oxide ores were nearly exhausted, nearly 700,000 tons had been shipped. From 1906 to 1910 about 125,000 tons of mixed carbonate and silicate was produced.
Manganese is also found in the Covadonga district, Province of Oviedo, where large boulders of manganese oxide are found in clay resulting from the weathering of underlying limestone. These deposits yielded 3,800 tons in 1915. Other productive deposits occur in the provinces of Seville and Teruel. Deposits are also known in the provinces of Ciudad Real, Murcia, and Almeria.
In Sweden, there are manganese ores north of Philipstad, in Wermland, where tabular bodies of manganese oxides are interlayered with dolomite and magnetite. These deposits contributed 7,607 tons out of a total of 7,733 tons in 1915, which was the maximum recorded production of Sweden.
Asia.
—In India, on the east coast in the Vizagapatam and Ganjam districts, Madras, is a unique group of rocks known as the Kodurite series, containing manganese garnet, manganese pyroxene, potash feldspar, apatite, and quartz. These rocks, supposed to be of igneous origin, have been deeply weathered and the manganese concentrated as oxides in the surface zone. The manganese ore bodies have been explored only to 100 feet in depth, but it is expected that they will extend to 500 feet. The largest ore body explored at the Garbham mine is 1,600 feet long and 100 feet wide, and, from 1896 to 1913, yielded 736,192 tons of ore. The Kodur deposit yielded 370,382 tons of ore from 1892 to 1913. Production began in 1892, reached a maximum of 111,501 tons in 1906, and slowly declined to 44,127 tons in 1913.
Manganese also occurs in the Balaghat, Bhandara, Chindwara, and Nagpur districts in the central provinces; Narukot and Panch Mahals districts, Bombay; Jhabua district, central India; and the Gangpur district in Bihar and Orissa. These districts form a belt that extends from Baroda, on the west coast, across northern India nearly to Calcutta on the east, a distance of 700 miles. In these districts, beds of manganese oxides with manganese garnet and rhodonite form a rock type known as gondite, which is interlayered with quartzite and mica schist. These rocks are considered to be sediments of the Dharwar group (Archean). The manganese oxides may have been laid down as sediments, or may represent the weathering of the silicates. The ore bodies are lenses and layers. The largest single deposit, Balaghat, has the form of a shallow trough, is 1³⁄₄ miles long and 45 to 50 feet thick, and yielded from 1901 to 1913, 725,248 tons of ore. In 1913, thirteen distinct deposits had yielded more than 100,000 tons each, the range being from 101,721 to 725,248 tons.
From 1901, when the deposits of this type were first exploited, the rate of production rose steadily to the maximum of 697,035 tons in 1913. During 1907, fifty-two separate deposits contributed 598,437 tons.
Where rocks of Dharwar age (Archean), such as mica schists, that do not seem to contain the manganese-bearing Gondite series, are deeply weathered, manganese and manganiferous iron oxides form irregular but locally extensive deposits on the crests of hills. These deposits are underlain by barren clays that represent the residue of the underlying rocks. The largest deposit yielded 160,000 tons of ore in three years, 1906 to 1908, but is probably almost exhausted. The principal deposits of this class are in the Sandur Hills district, Madras; the Shimoga district, Mysore; and the Belgaum district, in Bombay; which lie within an area less than 100 miles in diameter in southwest India. From 1905, when deposits of this group were first explored, the production increased to a maximum of 11,353 tons in 1909,then declined to 62,770 tons in 1913. The total yield of this group to the end of 1913 was only 765,401 tons.
As regards the commercial control of the manganese deposits, a law recently passed forbids aliens to own more than a minor interest in mineral deposits in India. Previous to this, during 1907, the latest year for which complete data are available and in which 899,055 tons was produced, the entire output was from mines owned by resident English or natives, except for 21,500 tons produced by the Carnegie Steel Co., of Pittsburgh, U. S. A.
The annual production of manganese ore in India rose steadily from 1892, when the first shipments were made, to 1907, when 899,055 tons was shipped; and since then has ranged from 450,000 to 815,000 tons. The total production, up to and including 1916, was 8,748,000 tons.