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. I on PI. 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 PI. 3. The figures are taken 

 from Dana's Minei-alogy. Figs, i and i a represent the ordinary crystals 

 as there found, while i <5 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 

 Mine7'alogy, 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 41-44 



Sulphur 17-84 



Iron, 32-94 



Cobalt, 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. jfaiir. Science, vol. i, xxiv, p. 386. 



