123 
TAB. -CCLXII. 
FERRUM« subsulphureum. 
Subsulphuret of Iron, or Magnetical Pyrites. 
Class 3. Metals. Order 1. Homogeneous. 
Gen. 7. Iron. Spec. Subsulphuret. 
Syn. Magnetical Pyrites. Hatchett in Phil. Trans. 
for 1804. 
Tue Rev. H. Davies of Beaumaris favoured me with 
these specimens from the foot of the mountain Moél Aha 
in Caernarvonshire, from whence some specimens were 
sent by the Hon. Colonel Robert Greville to his brother the 
Hon. Charles Greville, about the year 1798, as mentioned 
by Charles Hatchett, Esq., who has published so able an 
account of it, with the analysis, in the Philosophical 
Transactions for 1804, and from which I subjoin a part of 
the description, with a reference to the more perfect one. 
Mr. Hatchett observes that this Pyrites has been hitherto 
found only in some parts of Norway, Silesia, Bavaria, and 
at Mebendorf and Brichenbrun in Saxony. He found the 
British specimens to be magnetical, agreeing with others 
in every particular. A piece, nearly two inches square, 
acted upon the needle at a distance of four inches. The 
powder, which is blackish grey with but little metallic 
lustre, is immediately taken up by a common magnet, but 
the Pyrites does not act thus upon the powder, nor on 
iron filings, unless it has been placed for some time 
between magnetical bars: then indeed it acts powerfully, 
turns the needle completely round, attracts and takes up 
iron filings, and seems permanently to retain this addition 
to its original power. In the specimens which he obtained, 
the north pole was the strongest. 
From the appearance of those parts of the Magnetical 
Pyrites which have been exposed to the weather, it seems 
to be liable to oxygenizement, but not to vitriolization. 
