The Gold-Seeker's Manual (Paperback)

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: 51 CHAPTER IV. THE GEOLOGICAL POSITION OF GOLD IN VARIOUS ROCKS. Gold, which has hitherto been found either pure or alloyed only with other metals, usually occurs disseminated or distributed in minute quantities in the parent rock, which is generally either quartz or at least very quartzose. The metal is however by no means confined to this substance, being found also in clay-slate and limestone, as well as with granite and various other igneous and metamorphic rocks. It is usually associated with iron, often in the form of auriferous iron pyrites, sometimes with silver, tellurium and platinum, and occasionally with rarer metals such as palladium, iridium, osmium, rhodium, andc., which are chiefly interesting as mi- neralogical curiosities. Other minerals associated with gold are copper pyrites, blende, galena, and sulphur. The gold of commerce is obtained chiefly from sands and gravels produced from disintegration of the parent rock on the spot, or transported by water from districts where much gold is disseminated. Such sands, andc. contain amongst them fragments of gold consisting of lumps of various sizes. A quantity, small in proportion to the whole supply (not more than one-sixth), is also obtained from true mineral veins, in which gold is associated with veins of quartz in rocks usually schistose. The quartz in these cases is generally (but not always) cellular, rusty (from the presence of iron), and of loose texture; and the metal is usually disseminated also in the rock enclosing the vein, although perhaps not to any considerable extent. Few important and very profitable gold mines have been worked in veins, but the existence of large and little-worn lumps of gold in situ proves that this negative evidence must not be regarded as having any great value. At ...