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MINERAL TABLES FOR THE DETERMINATION OF MINERALS BY THEIR PHYSICAL PROPERTIES - 1906 - INTRODUCTION - THE natural method of identifying minerals is by using those characters which are prominent or which can be determined in the field or laboratory in the simplest manner. Practice in the determination of minerals by their physical prclperties tends to develop the habit of close and careful observation, and at the same time enables the student to acquire more lrnowledge of minerals in a given time than could be obtained by any other method. Experience has demonstrated that work in blowpipe analysis is less apt to become merely mechanical if it has been preceded by such practice. The tables include the common minerals and a few others of local prominence, which are generally considered as rare in occurrence. The minerals are arranged primarily according to streak and color, as seen in the Analytical Key, and under each color the arrangement is a. ccording to hardness. The tables differ from those of Weisbach chiefly in disregarding luster as an important division and in maintaining the same syztzm of arrangement throughout. Various works on mineralogv, especially Danas System of Mineralogy, have been consulted in the preparation of the tables. For valuable suggestions and criticisms the author is especially indebted to Professor Charles Palache of Harvard, who used the manuscript copies of the tables in the Summer School of the University of California. MINERAL TABLES. PHYSICAL PROPERTIES. THE only apparatus needed for the tables is a pocket-knife, a horse shoe magnet, a pocket-lens, a piece of unglazedporcelain or streak-plate, ancl a scale of hardness consisting of nine minerals. Thisscale can be procured of any mineral dealer or can be made up from specimens in an ordinary collection of minerals. Color.-The color of a mineral is perhaps the most important property usecl in its identification, yet it is the most difficult to acburately describe. A mineral may have but one characteristic color, or it may occur in various colors and shades consequently a mineral may be repeated several times in the tables. The color must always be judged by the fresh surface or fracture, and it should be homogeneous throughout the mineral. Vitreous minerals may often be discolored or st, ained bv v impurities, when they manifestly belong to the colorless or white class. Luster.-The luster of a mineral refers to the kind of reflected surface. The common kinds are metallic submetallic-imperfect metallic vitreous glassy adamantine brilliant oily luster resinous greasy pearly silky waxy. MINERAL TABLES. Streak.-The strea . k of a mineral is the color of its fine powder. It is C, O t L post 06, hla d Lv rubbing the specimen upon the streak-plate until a gefi iw tecodor is d o uced. 7 c Z c, L k I l a r d r i e s l hayr-d ness is meant the resistance that a mineral offers to abrasion or scratching. The relative hardness of n mineral is usually determined by scratching it successively by minerals or subst, ances of known, hardness, two minerals of the same hardness mutually scratching each other. The scale of hardness in common use, called t, he Mohs scale, in ascending degree of hardness, is as follows 1. Talc 2, Gypsum 3, Calcite 4, Fluorite 5, Apatite 6, Feltlspar 7, Quartz S, Topaz 9, Corundum 10, Diamond. The thumb-nail will scratch minerals up to 23, and the ordinary knife-blalde up to5 in the scale with n little practice the relative hardness of a mineral under G can be sipproximately determined Gth a knife-blade

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