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. 1898 edition. Excerpt: ... that when a number of small veins of mineral occur comparatively near together, which would not pay to work individually, it may ...Read MoreThis 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. 1898 edition. Excerpt: ... that when a number of small veins of mineral occur comparatively near together, which would not pay to work individually, it may be quite worth while to treat the deposit as a whole. Lenticular Aggregations.---Certain minerals, notably ironstones and manganese, are found occurring in masses which very frequently coincide with the bedding of the rock, but which thin out in all directions. They have probably been deposited during the formation of the rocks themselves, and are exceedingly capricious as regards their extent and mode of occurrence; for when one deposit has been worked out no guarantee whatever exists that any more ore will be found in the district. These lenticular aggregations vary in size from small patches only a few inches across, up to masses of many thousands of tons. Where minerals occur under these conditions, they have probably been precipitated from solution, in inland waters, by decomposing organic matter, such as wood or the leaves of trees, both of which are frequently found fossilised in beds of ironstone. At the present day there are deposits of iron ore being formed in some of the Norwegian lakes, and the peasants of the district earn a livelihood during the winter months by breaking the ice and dredging for the accumulated iron ore, which is removed from time to time. Irregular Masses include a great number of deposits, some of which are intimately associated with true fissure lodes, of which they appear to be offshoots; whilst others do not seem to be in any way connected with veins, although they have probably been formed in the same way as fissure lodes; others again are nothing more than shrinkage cracks produced during the cooling down of the eruptive rocks in which they occur. It may frequently be noticed in...Read Less
Copyright in bibliographic data and cover images is held by Nielsen Book Services Limited, Baker & Taylor, Inc., or by their respective licensors, or by the publishers, or by their respective licensors. For personal use only. All rights reserved. All rights in images of books or other publications are reserved by the original copyright holders.