Minerals in, Gneiss. 



399 



wrought for the preparation of copperas. In the gangue of the ore 

 occurs a mineral which exceedingly resembles peiiom, though it may- 

 be blue quartz. It deserves farther examination. 



Magnetic oxide of iron is sometimes met with in small disseminated 

 masses in gneiss, as in Athol and Shelburne. 



Arsenical sulphuret of iron is said to occur in Leicester in gneiss. 



In Pelham we meet in this rock, with well characterised specimens 

 of anthophyllite. 



'In that town, also, is a great abundance of finely crystalized 

 quartz. Some of the crystals are quite delicate. They are common- 

 ly limpid, though sometimes of a light brown color, and sometimes 

 of a fine topaz yellow, being genuine yellow quartz. Rarely are they 

 amethystine. Not unfrequently large cavities are drusy, and present 

 fine specimens. The crystals vary in size, from two inches in diam- 

 eter to the fineness of a sewing needle. It is not easy to ascertain 

 the precise situation of this quartz in the gneiss ; since it is seen only 

 in loose masses scattered over several acres. Probably, however, it 

 constitutes a vein. I observed no metallic substance in it, except a 

 little sulphuret of iron. 



Associated with this quartz are found beautiful specimens of ma- 

 millary chalcedony, (No. 1002.) Rarely it is of a milk white 

 color ; but commonly of a delicate blue. Sometimes it may be seen 

 investing distinct crystals of quartz, thus showing its origin to be 

 watery infiltration beyond all question. 



It has already been mentioned that steatite and serpentine occur in 

 beds in our gneiss. In Millbury, a variety of the former has been 

 found, which has been called vermiculite, on account of its singular 

 property of shooting forth vermiform masses, when exposed to heat ; 

 thus giving to the specimens, when in the fire, the appearance of 

 worms in motion. 



I have seen a specimen of gray copper from Brimfield ; and from 

 the geological constitution of that region, I infer that it originated 

 from gneiss. 



In Washington, Ct. the gneiss contains mesotype and stilbite ; and 

 at Bellows Falls, on the Vermont shore, a radiated mineral of the 

 zeolite family, with another in small and distinct crystals, which I 

 shall describe under greenstone, as a new species, by the name of 

 Lincolnite. 



