34 MINERALOGY AND LITHOLOGY. 
It is found massive, and also in beautiful crystals, that are well known 
to all mineralogists. 
The ordinary massive variety occurs abundantly. The quartzite and 
schists along the Connecticut river are often full of it, and it is sometimes 
an associate of the ores that have been proved to be auriferous. In these 
localities crystals of the ordinary form are also found. Large masses of 
the ‘non-crystalline variety are found at Jackson. Francestown, Haver- 
hill, Lebanon, Weare, Groton, Lisbon, Lyman, Middleton, and Alton are 
localities of note for this mineral. It is abundant in Rockingham county. 
The mineral, when crystallized, is commonly found in forms resembling 
Fig. 1 on Pl. 3. 
Arsenopyrite is orthorhombic in crystallization. The crystals that are 
found at Franconia are very remarkable for their form and for their per- 
fection. Some of them are represented on Pl. 3. The figures are taken 
from Dana’s Mineralogy. Figs. 1 and 1 4 represent the ordinary crystals 
as there found, while 1 4 is an exceptional variety, both in form and compo- 
sition. It was analyzed in 1833 by A. A. Hayes,* who, on account of the 
cobalt that it contained, considered it to be a new mineral, and named it 
danaite, in honor of Prof. J. F. Dana, who made known the locality, and 
who first detected the presence of cobalt in the mineral; but it having 
been shown that cobalt is at times present in varying amounts in arsen- 
opyrite, where it replaces a portion of the iron, Prof. J. D. Dana, in his 
Mineralogy, considers it to be merely a variety of that mineral, which is 
very evidently the case. The following is the analysis of the Franconia 
danaite, as made by Mr. Hayes: 
Arsenic, . 3 : ; 3 5 5 3 ‘ F . a 41.44 
Sulphur, . : . A 3 . A . . ‘ A 17.84 
Iron, - z 2 5 s 5 5 : ‘ . ; : 32.94 
Cobalt, . - . 5 . - - F ‘ é 5 6.45 
98.67 
These rare crystals are found isolated in the gneiss rocks, associated 
with chalcopyrite, and are highly prized by mineralogists and crystallog- 
raphers. 
* Am. Four. Science, vol. s, xxiv, p. 386. 
