No. 6. DEPARTMENT OF AGRICULTURE. 460 



that these are striated, tl)at is fine grooves or scratches will be 

 found. These, it will be further noticed are at right angles to each 

 other on adjoining faces or sides of the cube. 



COMPOSITION 

 Iron Pyrites or Bisulphide of Iron is a combination of sulphur and 

 iron; when pure, the sulphur percentage is 53.4%, while that of the 

 iron is 46.G%, It frequently contains copper, arsenic, nickel, cobalt, 

 gold or other minerals but in very small quantities. 



USES 



The principal use to which Pyrite is put is for the manufacture of 

 sulphuric acid. Formerly, sUlphate of iron or copperas was made 

 from it but, as this is now obtained as a by-product of a process of 

 galvanizing iron, the former method of producing it from pyrite has 

 been superseded. (A few years ago, more than half of the sulphuric 

 acid consumed in the United States was in the manufacture of super- 

 phosphates). Although this mineral is rich in iron, it is not used 

 as an ore in the furnace, because of the excessive amount of sulphur 

 it contains. Much of this injurious constituent can be eliminated 

 by roasting the pyrite before using. The residue, "Blue Billy," is 

 not, at the present time, considered a desirable ore for the manu- 

 facture of iron. The pyrite from some localities has, however, been 

 successfully treated and is. being used for the purpose. The "Blue 

 Billy," after being treated to remove as much of the contained sul- 

 phuric acid as possible, is used to some extent in the manufacture 

 of paint. It is not improbable, that before long, if not already, a 

 successful process or method of treating the "Blue Billy" to remove 

 its detrimental constituents will be found and its use in the manu- 

 facture of iron wiU be practicable and of economic importance. 



HOW TO DISTINGUISH IT 



The minerals for which iron pyrites may be mistaken are gold 

 and copper (the latter in the form of chalcopyrite) and pyrrhotite. 

 It will be found first, that the pyrite is harder than gold, as the former 

 can not, except with great difficulty, be scratched with a knife blade ; 

 the pyrite is brittle, while the gold is soft and can be readily cut 

 with a knife or hammered out into thin sheets. It differs from it 

 both in color and the color of its streak. Chalcopyrite which is a 

 sulphide of copper and iron can generally be distinguished from the 

 pyrite by its greater softness (3.5) and with the naked eye, by its 

 darker brassy color and its often irridescent tarnish, and the dif- 

 ference in its crystal forms. It is somewhat lighter in weight (specific 

 gravity 4.25). Chalcopyrite crystallizes in the tetragonal system but 

 is more frequently found as an ore mineral in irregular grains and 

 masses. The color of its streak is greenish black. 



Pyrrhotite or magnetic pyrites, another sulphide of iron, is some- 

 times mistaken for iron pyrites. It can readily be distinguished 

 from it, because: (1) it is much softer; (2) its color is of a bronze 

 rather than brassy yellow; (3) if it be broken into small pieces or 

 powdered, it will adhere to a magnet. Its streak is grayish black, 

 but, like the pyrite, it is brittle. Pyrrhotite may in turn be mistaken 



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