172 DESCRIPTIONS OF MINERALS. 
It is a constituent of nearly all meteorites, and the chief 
ingredient in a large part of them ; and in this state it is 
with a rare exception alloyed with nickel, and with traces 
of cobalt and copper. ‘The 'l'exas meteorite, of Yale College, 
weighs 1,635 pounds ; the Pallas meteorite, now at Vienna, 
originally 1,600; but one in Mexico, the San Gregorio 
meteorite, is stated to weigh five tons; and one in the dis- 
trict of Chaco-Gualamba, 8. A., nearly fifteen tons. Meteoric 
iron often has a very broad crystalline structure, long lines 
and triangular figures being developed by putting nitric acid 
on a polished surface. The coarseness of this structure dif- 
fers in different meteorites, and serves to distinguish speci- 
mens not identical in origin. Nodules of troilite (FeS), 
and schreibersite (iron phosphide) are common in iron me- 
teorites. Meteoric iron may be worked like ordinary malle- 
able iron. The nickel diminishes the tendency to rust. But 
some kinds contain iron chloride, or are open in texture, and 
rust badly. 
_ Pyrite.—Iron Pyrites. Iron Bisulphide. 

Isometric. Usually in cubes, the striz of one face at right 
angles with those of either adjoining face, as in fig. 1. Also 

