9 
iron. 387 
Geological Situation. It occurs in masses, veins and beds often of great extent, in pri¬ 
mitive, transition and secondary rocks. 
LOCALITIES. 
In regard to the localities of this ore in the State of New-York, I have nothing to add to the 
notice presented in the first part of this work (page 29 et seq.) 
IRON PYRITES. 
[From the Greek n'vp, fire; because it gives fire when struck with steel.] 
Fer Sulfure. Hauy. — Sulphuret of Iron. Cleaveland. — Iron Pyrites. Phillips and Shepard. — Bisulphuret of 
Iron. Thomson. — Hexahedral Iron Pyrites. Jameson. — Hexaedrischer Eisen Kies. Mohs. — Pyrite. 
Beudant. 
Description. Colour bronze yellow, rarely inclining to steel-grey ; 
sometimes brown, owing to decomposition. Streak brownish or green¬ 
ish black. It occurs regularly crystallized; also massive, dissemi¬ 
nated, globular and cellular. Cleavage parallel with the cube and 
octahedron, but most perfect with the former, which has hence been 
adopted as the primary, Fig. 448. Fracture uneven and conchoidal. 
Lustre metallic. Opaque. Brittle. Hardness from 6.0 to 6.5. Spe¬ 
cific gravity from 4.83 to 5.05. Before the blowpipe, it exhales a 
strong odour of sulphur, and yields a brownish globule, obedient to the magnet; and by con¬ 
tinuing the heat, it is converted into an uneven and crystalline black mass. 
It is much less hard than copper pyrites, which it sometimes resembles. From magnetic 
pyrites, it is distinguished by its want of action on the magnet. Some varieties are subject 
to spontaneous decomposition. 
Composition. Iron 47.85, sulphur 52.15 (Hatchett). Iron 45.15, sulphur 54.26 ( Ber¬ 
zelius ). 
There can be no doubt, therefore, that this is a compound of two atoms of sulphur and one 
atom of iron. Its proper chemical name, therefore, is Bisulphuret of Iron, and its formula is 
FeS 2 . 
Geological Situation. This mineral is found in almost all the different series of rocks. 
Uses. Iron pyrites is used in the manufacture of copperas, and of sulphuric acid. 
localities. 
Columbia County. The roof slate found at Hillsdale, contains abundance of cubic crystals 
of iron pyrites. These crystals undergo decomposition, and leave cavities in the slate. Mr. 
Mather remarks that this mineral, thus liable to decomposition, injures the slate, not only by 
causing cavities through which leakage takes place, but by changing its texture. 
