Outlines of Physical Geography Author:Edward Hughes 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: CHAPTER VII. Distribution Of Minerals. The general structure of the earth and features of its surface have been described in the preceding chapters, and we... more » are now prepared for an account of the most useful and valuable minerals which are found among its rock formations. Minerals are not distributed on the earth according to climates, like animals and vegetables ; but, by the kindness of Providence, those which are most necessary to man are found in almost all countries ; and others are more or less abundant, according to their importance. It is remarkable, also, that the most barren portions of the earth are often most plentiful in mineral treasures. The metals are sometimes found pure, but they are generally mixed with other minerals, in a stony substance, termed ore. They are found occasionally in beds, or large masses, but usually in veins, passing through rocks. The veins vary in width, from a few inches to many feet. Sometimes they extend many miles in length, varying in breadth in different parts. Their depth is often very great, but they are often neglected, because the ore is too poor, or the digging too expensive. Coal, salt, and iron, are frequently found in beds of great extent, but usually of no great depth. In digging an excavation, or mine, to procure any of these minerals, the course of the vein or bed is usually followed. The largest excavations are those of salt mines, some of which are several miles in extent. The deepest mine in Europe is the lead mine of Kuttenberg, in Bohemia, which is 3,000 feet in depth, but is now inaccessible. Some minerals are found upon the surface of the earth, mingled with its soil or sand, as is commonly the fact with gold and the precious stones. In this case, the mineral is procured by washing the sands. Metals. G...« less