⋙ Download Prospecting for Gold and Silver in North America Arthur Lakes 9781231596982 Books

Prospecting for Gold and Silver in North America Arthur Lakes 9781231596982 Books

Download As PDF : Prospecting for Gold and Silver in North America Arthur Lakes 9781231596982 Books

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1896 Excerpt ...in the decline of each volcanic outburst are marked by the appearance at the vent of certain acid gases. As the temperature at the vent declines, the nature of the volatile substances emitted undergoes a regular series of changes. In fumaroles, sulphurous acid and hydrochloric acid abound, with sulphureted hydrogen and carbonic acid in much smaller proportions. Around these fumaroles, deposits of sulphide of arsenic, chloride of iron and of ammonia, boracic acid, and sulphur take place. Arsenical pyrites are a common associate for the ores near the surface at Cripple Creek, and many rocks are permeated with iron pyrites. Where a volcanic vent sinks into extinction, hydrochloric and sulphurous acids are first evolved, and later sulphureted hydrogen and carbonic acid springs. Such springs are common in the volcanic districts of Colorado to-day, but we have long passed the stage of the stronger acids, which could only be expected in the pit of an active modern volcano like Kilauea. We may, however, expect to find traces left of these gases, in the rocks of Cripple Creek, such as a bleaching and decoloration of the rocks, leaching and precipitation of iron, forming those varied patterns of oxidation so common at every prospect hole; also deposits of various sulphates and chlorides, rocks deprived of iron and alkalies reduced to powdery siliceous masses. One action of subterranean springs is the transportation of material in a state of solution and redepositing of it elsewhere, especially in lines of relief of pressure, such as fissures, shattered rocks, and decomposed rocks and zones in the rocks. At Steamboat Springs, Nevada, metallic gold, cinnabar and other minerals have been found coating the sides of fissures from which living hot springs issue at the surf...