3iS Mr. Hatchett's Analysis 
Mr. R. Greville, in another part of his letter, states that 
copper ore has beep worked in several of the adjacent places, 
and that, many years ago, Capt. Williams, of Gian yr Avon, 
employed some miners at the place where this pyrites is found, 
but the undertaking proved unproductive. Yellow copper ore 
is certainly in the vicinity ; for some portions of it were adhering 
to the specimens which have been mentioned ; and 1 shall here 
observe, that the stone which accompanies the magnetical 
pyrites, is a variety of the lapis ollaris or pot-stone, of a pale 
grayish-green, containing smooth cubic crystals of common 
pyrites. 
§ HI- 
From the appearance of those parts of the magnetical pyrites 
which have been exposed to the weather, it seems to be liable 
to oxidizement, but not to vitriolization. 
The specific gravity, at temperature 65° of Fahrenheit, is 
4518. 
When exposed to the blowpipe, it emits a sulphureous odour, 
and melts into a globule nearly black, which is attracted by the 
magnet. 
500 grains, in coarse powder, were exposed, in a small earthen 
retort, to a red heat, during three^ hours. By this operation, the 
weight of the powder was very little diminished ; neither was 
there any appearance of sulphur in the receiver, which however 
smelt strongly of sulphureous acid. 
500 grains of the same were put into a flat porcelain crucible, 
which was kept in a red heat, under a muffle, during four hours. 
The powder then appeared of a dark gray, with a tinge of deep 
red, and weighed 432.50 grains. The loss was therefore 67.50 
