BISILICATES. 251 



Pargasite. Dark-green crystals, short and stout (resem- 

 bling fig. 4), with bright lustre, of which Pargas in Finland 

 is a noted locality. G. =3*11. 



Composition. Silica 45*5, alumina 14*9, iron protoxide 

 8*8, manganese protoxide 1*5, magnesia 14*4, lime 14*9 = 

 100. 



Hornblende. Black and greenish-black crystals and mas- 

 sive specimens. Often in slender crystallizations like actino- 

 lite ; also short and stout like figs. 4 and 5, the latter more 

 especially. It contains a large percentage of iron oxide, and 

 to this owes its dark color. It is a tough mineral, as is im- 

 plied in the name it bears. This character, however, is best 

 seen in the massive specimens. Pargasite and hornblende 

 contain both alumina and iron. 



Composition of a hornblende : Silica 48-8, alumina 7*5, 

 magnesia 13*6, lime 10 2, iron protoxide 18 8, manganese 

 protoxide 1-1 = 100. 



Obs. Hornblende is an essential constituent of certain 

 rocks, as syenyte, dioryte and hornblende schist. Actino- 

 lite is usually found in magnesian rocks, as talc, steatite or 

 serpentine ; tremolite in granular limestone and dolomite ; 

 asbestus in the above rocks and also in serpentine. Black 

 crystals of hornblende occur at Franconia, N. H., Chester, 

 Mass., Thomastown, Me., Willsboro', N. Y., in Orange 

 County, X. Y., and elsewhere. Pargasite occurs at Phipps- 

 burg and Parsonsrield, Me.; glassy actinolite, in steatite 

 or talc, at Windham, Eeadsboro', and New Fane, Vt., 

 Middlefield and Blandford, Mass.; and radiated varieties 

 at the same localities and many others. Tremolite and 

 gray hornblende occur at Canaan, Ct., Lee, Newburgh, 

 Mass., in Thomaston and Eaymond, Me., Dover, Kings- 

 bridge, and in St. Lawrence County, N. Y. ; at Chestnut 

 Hill, Penn. ; at the Bare Hills, Md. Asbestus at many of 

 the above localities ; also Brighton and Sheffield, Mass. ; 

 Cotton Rock and Hustis's farm, Phillipstown, N. Y., near 

 the Quarantine, Richmond County, N. Y. Mountain lea- 

 ther is met with at Brunswick, N. J. Edenite, a white 

 aluminous kind, occurs at Edenville, N. Y. 



Asbestus is the only variety of this species of any use in 

 the arts. The flax-like variety is sometimes woven into 

 fire-proof textures. Its incombustibility and slow conduc- 

 tion of heat render it a complete protection against the 

 flames. It is often made into gloves. A fabric when 



