C 315 a 
XII. An Analysis of the magnetical Pyrites; with Remarks on 
some of the other Sulphurets of Iron. By Charles Hatchett, 
Esq. F. R. S. 
Read May 17, 1804. 
§1. 
o f the various metallic sulphurets which constitute one of the 
grand divisions of ores, none appear to be so universally dis- 
persed throughout the globe, as the sulphuret of iron, commonly 
called Martial Pyrites ; for the species and varieties of this are 
found at all depths, and in all climates and soils, whether 
ancient, or of alluvial and recent formation. It is remarkable 
also, that, under certain circumstances, this sulphuret is daily 
produced in the humid way; an instance of which, a few years 
back, I had the honour, in conjunction with Mr. Wiseman, to 
lay before this Society ; * and although, in regard to pecuniary 
value, the pyrites of iron may be considered as comparatively 
insignificant, yet there is every reason to believe, that in the 
operations of nature, it is a substance of very considerable 
importance. 
§n. 
The species and varieties of martial pyrites, are in general so 
well known, and have been so frequently and accurately de- 
scribed, as to figure, lustre, colour, and other external characters^ 
* Phil. Trans, for 1798, p. 567, 
