Page:Encyclopædia Britannica, Ninth Edition, v. 4.djvu/268

224 106 and 113 Fahr. These arc at an elevation of about 6000 feet above the sea.

The metallic and mineral products which occur in the geological formations above described are very various. Diamonds were first discovered in the Serra do Espinhaco, in the vicinity of Diamantina, about 300 miles north of Rio, in 1786. In this neighbourhood there are shales, sandstones, and conglomerates ; upon the sandstone there is or was a stratum of quartzite, still very distinct in many places, and among the sands created by the disintegration of this rock, diamonds are found. This district is named the Ckapada of Diamantina, a term applied to small elevated plateaus, usually consisting of horizontal deposits, and sepa rated by deeply eroded valleys. The diamond-producing soil extends along the Serra do Espinhago as far as the northern borders of the province of Minas, along the valley of the upper Belmonte, and in the interior of the province of Bahia, as well as in the mountains that lie south-west of the sources of the Sao Francisco. Diamonds of smaller value have also been found in the province of Goyaz (on the Rio Claro) ; in Ma tto Grosso, where the valley of the Paraguay about Cuyabci and Diamantino has diamonds in considerable abundance ; in Parana., on the Rio Tibagy, a tributary of the Parani-Panema ; in Sao Pedro do Rio Grande do Sul ; and in Sao Paulo ; but the area of their distribution is far from being well ascertained. The dia monds are generally obtained by washing; an excavation is made to reach the stratum called cascalho, a gravel com posed principally of quartz and fragments of different rocks of the neighbourhood, and mixed with a reddish clay. The washers are seated either by a pond or running stream, and a portion of the gravel, being thrown into a large shallow wooden pan, is mixed with water and stirred about in the current, so that the muddy water escapes and the gravel and sand remain. This is now passed through a sieve, which separates the larger gravel from the smaller ; the pebbles are then picked out, and the overseer examining the sand easily selects any diamonds that may be present. The diamonds are often of considerable size. Burton mentions one found in the Chapada of Bahia weighing 76

One of the Brazilian coal basins lies in the province of Santa Catharina, between the plateau and the sea; and along the banks of the Tubarao, beds of bituminous coal of fair quality are exposed, and were first noticed in 1841. Three separate coal-fields have been traced in the province of Rio Grande do Sul : the largest is situated in the valley of the Jaguarao (the boundary river with Uruguay), and in that of the Candiota, covering an area of about 50 miles by 30 miles ; the second occurs in the valley of a tributary of the Rio Jacuahy, near the centre of the pro vince; and a third near the village of Sao Jeronymo, on the bank of the Jacuahy. The Candiota field is now being- worked by an English company. At the Arroyo dos Ratos in the same province, mines have been worked on a small scale, the coal from which is used by the steam-boats which ply on the Lagoa dos Patos, or on the rivers. Bitumen is found in most of the provinces, and is worked near the south coast of the province of Bahia.

Sulphur exists in a native state in the province of Rio Grande do Norte, and in small quantity in Rio Grande do Sul, as well as at Furquim. and Corrego do Ouro, in the district of Minas Novas in Minas Geraes. Saltpetre occurs with salt over a large area of Minas Geraes and Bahia, but is also abundantly formed in the floors of the calcareous caves of the Rio Sao Francisco valley from ihe city of Ouro Preto downwards. Saline efflorescence is observed at innumerable localities in the drier portions of the Brazilian plateau ; efflorescences of nearly pure sul phate of magnesia are also to be found in the valley of the Rio das Velhas in the Sao Francisco basin, and in the province of Ceara, where chloride of sodium also appears.

Gold in Brazil is found in quartz veins traversing the old metamorphic rocks, such as clay-slate, mica-slate, or iron schist, in drift gravels and clays, and in alluvial sands and gravels derived from the wear of these. Most gold is afforded by the clay-slates traversed by auriferous quartz lodes, by the rock called Itacolumite (metamorphic rock of Lower Silurian age), and by certain iron ores known as Itabirite and Jacutinga, the latter described by Burton as a substance composed of micaceous iron schist and friable quartz, mixed with specular iron oxide of manganese and fragments of talc. Over a very large area of the province of Minas Geraes, in the vicinity of Ouro Preto, the country is auriferous, and here are the richest gold mines of Brazil. The celebrated Morro Velho mine is situated on the western side of the valley of the Rio das Velhas, not far from Sabard, and was at first worked by native miners, but afterwards with great success by a company. The mines of Gongo Soco lie about 20 miles east of Morro Velho, on the opposite side of the Velhas, and were at one time very productive. Another company owns a tract of 21 square miles, not far from the Morro Velho. Other mines have been worked in this neighbourhood at the Morro de Sta Anna,, at Maquin6 near it, and in the Serra of Cata Branca, 2 miles east of the village of Corrego Seco. These mines with two exceptions have proved failures in working, after a period of success, and this notoriously from bad management. The mines, however, are very far from being exhausted ; indeed the underground wealth of the country is as yet almost untouched. Much of the remaining portion of the province of Minas, and especially the upper basin of the Sao Francisco, is auriferous. In Northern Brazil the only gold mine yet opened is that cf Tury-assu in the province of Maranhao ; but concessions for working gold have been granted by Government in many parts of the provinces of Bahia, Pernambuco, Parahyba, Piauhy, Goyaz, Ceara, and S. Paulo. In southern Brazil gold is known at Caapava, Rio Pardo, Sta. Maria, and Cruz Alta, in the province of Rio Grande do Sul ; and at the first-named locality a Brazilian company is carrying on the work of mining. Gold washings occur in almost every province, but especially in the district of Minas Novas, 200 miles north of Ouro Preto, where the metal is found in grains or nuggets in a cascalho of quartz pebbles, often cemented into a conglomerate by iron oxide. They are carried on, however, in the rudest and most irregular way, and with more modern appliances might prove very remun erative.

The gold of Brazil is always alloyed with silver, and this metal is present in many of the galenic formations which are known in almost every province, as well as with the copper in the mines of Rio Grande do Sul. At the hill of Ara^oiva, in the municipality of Sorocaba in Sao Paulo, silver was extracted nearly two centuries ago. Rich mines of mercury occur in the province of Parand not far from the capital. Copper is abundant in the provinces of Matto Grosso, Goyaz, and Minas, near the capital of Bahia, in Maranhao and Ceard, but chiefly in Rio Grande do Sul, where at Santo Antonio das Lavras, in the municipality of 