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Updated: June 26, 2025
Ordinary metalliferous Veins or Lodes. Their frequent Coincidence with Faults. Proofs that they originated in Fissures in solid Rock. Veins shifting other Veins. Polishing of their Walls or "Slicken sides." Shells and Pebbles in Lodes. Evidence of the successive Enlargement and Reopening of veins. Examples in Cornwall and in Auvergne. Dimensions of Veins.
This group, however, is a hundred leagues long and eighty broad; and though wherever M. Bonpland and I traversed this vast group of mountains, its structure seemed to us extremely uniform, it would be wrong to affirm that it may not contain very metalliferous transition rocks and mica-slates superimposed on the granite.
A windlass is in the centre of the chasm; and it is by means of this windlass that the metalliferous substance is raised to the surface in square wooden boxes. Here the dressing of the ores commences; boys cluster in all directions, under the wooden shed, and in oilier sheds beyond that.
The whole district, from the sea to the Cordillera, is more or less metalliferous; and I heard of gold, silver, copper, lead, mercury, and iron veins. The metamorphic action, even in the lower strata, has certainly been far less here than in Central Chile.
These effects are common to all granitic table-lands, at the Harz, in the metalliferous mountains of Bohemia, in Galicia, on the limit of the two Castiles, or wherever a granite of new formation appears above the ground. The rocks, which are at distances from each other, are composed of blocks piled together, or divided into regular and horizontal beds.
The prospector holds the end of an arm in each hand, with the point of the V directed forward horizontally, and as he walks along, the point turns down whenever he comes over a metalliferous vein, metallic body or water. It is supposed that very few persons can use the divining rod effectually; for most men it refuses to turn.
Although the precise age of such copper lodes can not be defined, we may safely affirm that they were either filled at the close of the Silurian or commencement of the Devonian period. Besides copper, lead, and silver, there is some gold in these ancient or primary metalliferous veins.
Metalliferous veins referable to such agency are occasionally a few inches wide, but more commonly three or four feet. They hold their course continuously in a certain prevailing direction for miles or leagues, passing through rocks varying in mineral composition. Vertical sections of the mine of Huel Peever, Redruth, Cornwall. Vertical section of the mine of Huel Peever, Redruth, Cornwall.
We have no evidence that any volcanic eruption has drawn its material from zones or magmas especially rich in metals or their ores, and on the contrary, volcanic districts, like those mentioned, and regions, such as the Sandwich Islands, where the greatest, eruptions have taken place, are poorest in metalliferous deposits.
On the other hand, the veins which traverse stratified rocks are, as a general law, more metalliferous near such junctions than in other positions.
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