392 



DESCRIPTIVE MINERALOGY. 



MAGNETIC IRON PYRITES. 



Pet Sulfilt^ Perrifere. Haay. — Magnetic Sulphuret of Iron. Cleaveland. — Magnetic Iron Pyrites. Phillips 

 and Shepard. — Magnetic Pyrites. Thtrmson. — Rbombohedral Iron Pyrites. Jameson. — Rbomboedrischer 

 Eisen-Kies. Mohs. — Leberkise. Beudant. 



^'t- *^- Description. Colour intermediate between bronze-yellow and cop- 



per-red ; speedily tarnishes on exposure to the air. Streak dark grey- 

 ish black. It rarely occurs crystallized ; usually massive and disse- 

 minated. Primary a regular six-sided prism, Fig. 463. Cleavage 

 parallel with the terminal planes ; less distinct parallel with the lateral 

 ones. Fracture uneven, passing into conchoidal. Lustre metallic. 

 Opaque. Brittle. Hardness 3.5 to 4 . 5. Specific gravity 4 . 63. It 

 acts slightly upon the magnetic needle. Before the blowpipe, sulphur 

 is evolved, and it melts into a blackish globule which is obedient to 

 the magnet. It is almost entirely soluble in muriatic acid, with the 

 evolution of sulphuretted hydrogen gas. 

 This mineral differs from common iron pyrites in its peculiar colour, its liability to tarnish, 

 and in its being slightly magnetic. 



Composition. Iron 63.50, sulphur 36.50 {Hatchett). Iron 60.32, sulphur 38.78 (Rose). 

 Iron 59.85, sulphur 40.15 (Stromeyer). 



Haiiy supposed that this mineral is a common sulphuret of iron, mixed with a little metallic 

 iron. The proportion of the latter, however, must be quite variable, and its true atomic com- 

 position has not been accurately determine^. It is probably FeS + F^aSs. 



Geological Situation. Magnetic pyrites is usually associated with magnetic iron ore in 

 rocks of the primary series, especially granite and gneiss. It has not been met with in much 

 abundance in this State. 



Uses. This mineral is, like the preceding, employed in the manufacture of copperas and 

 sulphuric acid. 



LOCALITIES. 



Essex County. Masses of magnetic iron pyrites of some size have been found about a 

 mile and a half north of Port Henry, on the land of Mr. A. Stone. It has the peculiar tar- 

 nish of that mineral, is strongly attracted by the magnet, and possesses polarity in a high 

 degree. It may be mixed with a small proportion of magnetic iron ore. 



Lewis County. Near Natural bridge in the town of Diana, small masses are found in an 

 aggregate of mica, quartz and carbonate of lime. 



Orange County. This mineral occurs, usually associated with the magnetic iron ore, at 

 the O'Neil mine, the Rich iron mine, near Greenwood furnace, and in other parts of the town 

 of Monroe. The specimens are massive, and usually have a pale yellowish colour. Small 

 fragments are attracted by the magnet, but not so powerfully as the specimens from Essex 

 county, nor do any of them possess polarity. 



