Large deposits of low-grade manganese ore also occur in the Leadville district in Colorado, where irregular bodies of iron-manganese carbonate have replaced magnesian limestone of Carboniferous age and are weathered to oxides to depths as great as 850 feet. From 1885 to 1918, the total production was 3,202,678 tons of material, most of which contained from 15 to 30 per cent. manganese. Other deposits of ferruginous manganese ore have been exploited in Eagle County, Colorado; the Pioche district, Nevada; Silver City district, New Mexico; and in Arkansas, Georgia, and Virginia. In _Canada_, large deposits of siliceous manganese ores occur in Newfoundland, and several small deposits in New Brunswick, Alberta, and British Columbia. In _Costa Rica_, manganese occurs in four districts near Playa Real, Nicoya Peninsula, in the form of oxides that seem to be interlayered with sedimentary rocks. The most productive deposits are owned by citizens of United States and of Cuba; others are owned entirely by Cubans. They were first exploited in 1916, and to the end of 1918 had exported 18,000 tons to United States. In _Cuba_, manganese is mined near Santiago and Bueycito, in the province of Oriente. Near Santiago, manganese oxides occur as lenticular or irregular bodies in tuff, clay, and limestone. Other deposits are reported in Santa Clara and Pinal del Rio provinces. The mines that have been the source of more than 90 per cent. of the exports are owned jointly by citizens of Cuba and of the United States, and the remaining mines by Cubans. From 1888 to 1910, 266,621 tons were exported. In 1915, after four years of idleness, the mines were reopened, and imports into the United States from 1915 to 1918, inclusive, were 163,189 tons.[52] [52] Production data, long tons, unless otherwise specified. In _Mexico_, manganese ores are found four miles north of Chihuahua City and south of Palomas, in the State of Chihuahua. It is assumed that the deposits are owned by native Mexicans. Manganese also occurs near Conception Bay, Lower California, where the mines are owned by native Mexicans but are under lease to Americans. From both of these districts, 1,500 tons were produced and exported to the United States in 1917. In the Republic of _Panama_, near Nombre de Dios and Madinga, there are irregular lenses of manganese oxides in decomposed sedimentary beds. Seven groups of deposits were exploited near Nombre de Dios. Five of them were exploited by Americans, one by native owners, and one by French. The Nombre de Dios deposits yielded 50,000 tons of ore from 1871 to 1902, largely during the last six years. The Madinga deposits were opened in 1916 and during 1916 and 1917 exported 11,000 tons to the United States. =South America.=--The largest deposits of manganese ore in South America are in _Brazil_, and especially in the important mining state of Minas Geraes.