26 
ON PYRTTE AND MARCASITE. 
[bui.i,. 186. 
visible impurity and showing characteristic crystallization. Other 
specimens, which were found to contain pyrite, are described in a 
later section. 
Values of p for various samples of marcasite. 
No. 
6 
Locality. 
Dover Cliffs. England 
Galena. Ill 
8 Galena. Ill 
9 
10 
11 
12 
13 
1! 
Linden mine, Wis .. 
Galena, 111 
Hazel Green, Wis . . 
Weardale. England. 
Cornwall, England . 
Webb City, Mo 
Density. 
4.881 
4. 891 
4.901 
4.886 
4.896 
4.880 
4.878 
4.887 
P- 
16.3 
16.9 
16.1 
16. 5 
26.7 
16.3 
16.9 
17.4 
17.3 
18.1 
17.5 
18.0 
18. 
18.7 
18.3 
18.6 
18.8 
Mean valiu 
of p. 
16.3 
16. 5 
16.6 
16. 6 
17.4 
17.8 
18.0 
18.5 
18.7 
No. 6. This is the specimen described by Julien ' as follows: " No. 14. Marcasite, 
Dover Cliffs, England. A brilliant cluster of spearheaded crystals— broad, stri- 
ated, twinned plates— embedded in light gray chalk, grayish white and brilliant 
on fracture." Some of the crystals carry small pyrite crystals along the plane of 
twinning, which are visible only after cleaning with acid. Only those free from 
visible pyrite were used for the determination. 
No. 7. A hollow stalactite from Galena, 111. The inner portion is fibrous, the 
outer columnar, with pyramidal terminations. Tarnish, copper colored. Color 
of fresh fracture or clean surface, tin white. It contains a trace of copper and is 
free from arsenic. Only the outer columnar portion was used. 
No. 8. A similar stalactite from Galena, 111., with greenish gray tarnish on 
fracture and bronze colored on surface and with decided vitriolization. 
No. 9. Curved wedge-shaped crystals of the Joplin type, from Linden mine, 
Wisconsin. Iridescent blue and yellow tarnish. Fracture, tin- white. The speci- 
men carried a little galena and calcite, from which it was carefully freed by acid 
and by picking out. Analysis showed a trace of copper and a little lead. 
No. 10. Galena. 111. A compact mass of large acute pyramidal crystals branch- 
ing out from a common axi3. Tarnish, greenish yellow. Color on fresh fracture 
and on green surface, tin-white. A few crystals of chalcopyrite. Material care- 
fully selected for determination gave traces of silica and copper and no arsenic. 
No. 11. Hazel Green, Wis. A thick crust on calcite. with distinct rhombic 
crystallization. Color, tin- white. Contains traces of lead and copper and is free 
from arsenic. 
Annals New York Acad. Sci., Vol. IV, 1887, p. 172. 
