MINERALOGY

A branch of physico-chemical science, which teaches the properties, composition, and relations of mineral bodies, and the art of distinguishing and describing them. " There is no branch of science," says Sir J. Herschcl, " which presents so many points of contact with other departments of physical research, and serves as the connecting link between so many distant points of philosophical ■peculation, as this. To the geologist, the chemist, the optician,the crystallographer, it offers especially the very elements of their knowledge, and a field fix many of their curious and important inquiries; nor, with the exception of chemistry, is there any which has undergone more revolutions, or been exhibited in a greater variety of forms. To ilie ancients it could scarcely be said to be at all known; and, up to a comparatively recent period, nothing could be BOre imperfect than its descriptions, or mure inartificial and unnatural than its cla ifications. The more important minerals in the arts, indeed— those used for economical purposes, and those from which metals were extracted — had a certain degree of attention paid to them for the sake of their utility and commercial value, and the precious for that of ornament; but until their crystalline forms were attentively observed, and shown t<r*be determinate characters, on which dependence could be placed, no mineralogist could give any correct account of the real distinction between one mineral and another. It was only, however, when chemical analysis had acquired a certain degree of prevision and universal applicability, that the importance of mineralogy as a science began to lie recognised, and the connexion between the external characters of a stone and its ingredient constituents brought into distinct notice." In the above quotation, the two characters of minerals upon which their cla ification is founded are adverted to, namely, their structure and their composition; and, pursuing these as their leading objects, mineralogists have of late discarded a number of other qualities upon which much Ureas was formerly laid, but which are so variable and indefinite as to be really of little value; such, for instance,as weight, colour, touch, nnd other sensible qualities, which often vary in different specimens of the same mineral. There are so many disadvantages belonging to any mineralogical arrangement founded exclusively on crystalline form, or on chemical composition, that, for all practical purposes, it is nece ary to blend the two; but since the chemical theory of definite proportionals, or, as it is commonly called, the atomic theory, has been shown to be applicable to the greater number of mineral combinations, the chemical arrangement of mineral substances has a umed a new and Important aspect: it being o'f course nece ary, in describing a mineral, that its crystalline form and modifications should in all cases form an e ential part of such description, where at least it can be attained; for it must be recollected that there are many cases in which minerals do not occur crystallized, and where that characteristic, therefore, would be totally at fault. It has been well observed by Dr. Thomson (System of Chemistry, Part III., Introduction), "that if mineralogy were to be confined to mere crystallized bodies, it would be divested of the greatest part of its utility; for a very great proportion of those minerals that are of the greatest utility to man, and which, therefore, it is peculiarly important to be able to distinguish from others, are seldom found in the state of regular crystals. How often do the ores of copper, tin, lead, and iron occur in an amorphous state 7 And were a mineralogist incapable of distinguishing them from each other, and from other minerals, except in the rare cases when they a ume a regularly crystallized form, his knowledge would be usele , as far as the important arts of mining and metallurgy are concerned." Mincrnlogieal analysis, as connected with the atomic theory, has made no inconsiderable progre in the skilful and industrious hands of Berzelius; but it is still quite in its infancy as regards the foundation of a mineral arrangement;and, before it can be succe fully adopted as such, many new analyses, and much laborious revision of former researches, will be requisite. One of the latest authors on mineralogy, who has adopted an arrangement founded upon the chemical composition of minerals, is Dr. Thomas Thomson. He divides minerals into three cla es: III. Silicon? IV. Phosphorous. V. Sulphur 1 VI. Selenium. VII. Tellurium.... 1 VIII. Arsenic 5 IX. Antimony 5 X. Chromium. XI. Molybdenum 1 XII. Tungstein. XIII. Columbium. XIV. Titanium. XV. Vanadium. II. Alkaline Bases I. Ammonia 2 II. Pota ium 1 III. Sodium 7 IV. Lithium. V. Barium 5 VI. Strontium 6 VII. Calcium 30 VIII. Magnesium 37 IX. Aluminum. 1. Pure, or combined with bases. 7 2. Simple salts 24;i. Double anhydrous salts... 39 4. Double h vdrous salts, soluble in water 3 5. Double, insoluble in water, and phosphates 4 C. Double hydrous aluminous silicates, or zeolites 39 7. Triple aluminous salts... 15 8. Quadruple aluminous salts.. 12 X. Cluciniun 4 XI. Yttriimi 6 XII. Cerium 8. XIII. Zirconium 5 XIV. Thorinum 1 XV. Iron.1. Uncombincd, or united to a sin. pie substance 13 2. Oxygen salts of iron... 22 Double ditto 10 Triple ditto G 3. Sulphur salts of iron.. 2 XVI. Manganese, 1. Combined with simple. bodies. II 2. Simple oxygen salts... 5 3. Double oxygen salts... 5 4. Triple oxygen salts... 1 XVII. Nickel. 1. Combined with simple bodies 5 2. Oxvgcn salts 1 3. Sulphur salts 2 [s. 765]