Author: W. F. P. McLintock
Publisher:
Published: 2015-08-06
Total Pages: 102
ISBN-13: 9781332350582
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Excerpt from Guide Collection of Gemstones: Museum of Practical Geology The minerals in the Museum of Practical Geology are arranged for the most part according to their commercial applications and, in consequence, the ores, i.e., minerals used for the extraction of metals, are separated from the so-called non-metallic minerals or those which, in general, are not applied to such a purpose. This arrangement has, of course, no scientific basis and fails to bring out the relationships between the various species, but it possesses the advantage of showing in a compact and readily accessible way those minerals which concern commercial and mining men. The non-metallic minerals are arranged in cases, marked A - X. The term non-metallic is somewhat misleading, as nearly all the minerals to which it is applied contain a metal or metals. These, however, are usually the light metals, e.g., aluminium, calcium, magnesium, potassium, sodium, as distinguished from the heavy metals of commerce, such as copper, tin, silver, gold, lead, &c. Amongst the non-metallic minerals gemstones occupy an important place from the point of view of commercial and general interest. They have not been separated from the rest of the minerals of this class, and the visitor will find them distributed throughout the various divisions. The reason for this is that in the majority of cases gemstones show no natural relationships with one another, the only feature which unites them into a class being their suitability for purposes of adornment. This suitability depends mainly on beauty and durability, but all minerals possessing these qualifications would not be reckoned as gemstones by a dealer. Many stones possessing these qualities in a high degree have little or no value at the present time, for there is a wide distinction between a stone naturally fitted for the purposes of the jeweller, and one for which there is a demand. From the commercial point of view the really precious stones are diamond, ruby, sapphire, emerald, and, perhaps, opal and turquois. (The pearl, although probably the most valuable gem at the present time, is excluded, as it can hardly be termed a mineral.) The demand for the first four of these is fairly constant and the value is always high for good specimens. The fashion of the moment dictates the value of the other minerals which legitimately claim a place amongst gemstones. At one time it may be tourmaline, at another, chrysolite, at another, cat's-eye, or aquamarine, or topaz, or zircon, which is in vogue; the favoured gem consequently rises in value until some new whim relegates it to comparative obscurity. To such stones the term "semi-precious" is sometimes applied. The element of rarity plays, perhaps, the most important part in determining the value of a gemstone and outweighs, by what often seems a disproportionate amount, considerations of beauty and of durability. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.
