i88 
Count de Bournon’s Description of 
SECTION II. 
ARSENIATES OF IRON. 
Muttrell mine, which is immediately contiguous to Huel 
Gorland mine, in the county of Cornwall, has produced some 
specimens of arseniates of copper, exactly similar to those de- 
scribed in the former part of this Paper. But this mine is still 
more interesting to mineralogists, on account of a combination 
found therein, of arsenic acid with iron, and also a double com- 
bination of that acid with both iron and copper. 
The first mentioned of these arseniates seems analogous to those 
crystals, or cubes, of a fine green colour, of which some spe- 
cimens had already been found in Carrarach and Tincroft mines, 
and which Klaproth, in his Memoir upon the Mineralogy of 
Cornwall, considered as belonging to the arseniates of copper ; 
but, according to the analysis made by Mr. Chenevix, with 
all the care which his extensive knowledge and extreme zeal 
for science would naturally lead him to employ, it appears to 
be a true arseniate of iron, containing only a small quantity 
of copper ; and even that quantity seems to be merely an acci- 
dental mixture. As, in the specimens from the old mines of 
Tincroft and Carrarach, the greatest part of the crystals ad- 
hered to vitreous grey copper ore, it is possible that some par- 
ticles of that ore remained attached to the crystals ; or, as I 
have frequently found to be the case, that some such particles 
had penetrated into the crystals, and that Mr. Klaproth had 
been thereby deceived, by finding in the button left by the 
blow-pipe, a much greater proportion of copper than this ore 
