COMMON MINERALS AND VALUABLE ORES. 



THEO. F. BROOKINS. 



I. IRON MINERALS. 



PROBABLY many a bright youth, 

 accustomed to wander through 

 the fields in enjoyment of na 

 ture, has been thrilled with 

 pleasurable anticipations on finding, in 

 some outcrop of crystalline rock, a 

 mineral substance that glittered as 

 gold. That his anticipations were pre 

 mature should not deter the ambitious 

 youth. Men far beyond him in expe 

 rience have been deceived by that same 

 "fool's gold." History records that 

 shiploads of the valueless yellow iron 

 pyrites were sent to England by ex 

 plorers of America on the supposition 

 that they were accumulating gold. 



Of the various compounds of iron 

 occurring in nature, but four may be 

 considered as relatively common py- 

 rite, magnetite, hematite, and limonite. 

 Pyrite consists of iron and sulphur; 

 magnetite, hematite, and limonite are 

 oxides of iron. The first-named min 

 eral differs largely from the others in 

 external appearance as well as in com 

 position. The others are, however, 

 readily differentiated. We will dis 

 cuss each of the four minerals in the 

 order mentioned above. 



The sulphide of iron, pyrite, occurs 

 in many crystalline rocks; but, owing 

 to the difficulty of separating the iron 

 and sulphur, is not used as an ore of 

 iron. The mineral much resembles in 

 external appearance a yellow ore of 

 copper, called chalcopyrite, from which 

 it may be distinguished in that it will 

 strike fire with steel. A specimen of 

 pyrites containing large crystals is an 

 interesting subject of study. These 

 crystals are cubical in shape, but gen 

 erally massed together so that no sin 



gle crystal form may be observed as 

 complete. Peculiar striations on the 

 cube faces may often be noted. The 

 striations of no two adjoining faces 

 are continuous; but rather a striation 

 of one face bears to that of another in 

 direction the relation of the stem of a 

 printed T to the top, or vice versa. 

 Owing to the affinity of each compo 

 nent element for oxygen, pyrite often 

 changes to vitriol, or else forms the 

 oxide of iron, limonite, described be 

 low. 



The black oxide of iron, ma-gnetite, 

 occurs widely distributed. As its name 

 indicates, it sometimes displays the 

 properties of a magnet. If a frag 

 ment of unequal dimensions be sus 

 pended freely by a string, the longer 

 dimension will gradually swing into a 

 north and south direction. The prop 

 erty possessed by magnetite of attract 

 ing other bits of iron appears to have 

 been known to the ancients, and by 

 them the name lodestone was applied 

 to the mineral. Since the power to 

 attract other particles of iron is not 

 apparent in all specimens of magnetite 

 we must consider other more distin 

 guishing characteristics. The ore is 

 very heavy; particles of it are attracted 

 by an artificial magnet, in which re 

 gard it differs from the other minerals 

 we have mentioned; if a piece of the 

 ore be scratched across the surface of 

 a harder substance, e.g., smoky quartz, 

 a black "streak" will be left. Pure 

 magnetic iron ore is intensely black, 

 with no coloring. 



In a series of ore beds formerly 

 operated by a mining company of 

 northern New York, four distinctions 



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