Geology, cf^c of the Connecticut. 215 



inches in diameter, the outer extremity of which presents 

 the form of the prism. I am rather disposed to beheve that 

 these cavities were once filled by a mineral not differing 

 much from the Thomsonite of Dumbarton in Scotland. 



Some varieties of quartz occur along the primitive region 

 of the Connecticut that can hardly be referred to any of the 

 preceding. Thus, there is a variety very abundant in beds 

 and tuberculous massifs in mica slate and argillite, which 

 differs in nothing from limpid quartz, except that it is color- 

 ed crimson red ; and perhaps it ought to be referred to fer- 

 ruginous quartz; but it differs from that commonly so cal- 

 led. Another variety is abundant every where, in large 

 rolled masses, of a reddish grey color when broken, with a 

 chonchoidal uneven fracture — the structure being almost 

 granular, and the aspect considerably like hornstone. Anoth- 

 er variety, more rare, occurring in pudding-stone, is of a 

 light blue color, and scarcely translucent ; but it can hard- 

 ly be called the blue quartz of mir;eralo;;ists. Another va- 

 riety is found in granite and in loose masses, and is nearly 

 black, and only semi-transparent. Another variety has a 

 tinge of yellow — another of green, &ic. 



16. Amethyst. At Wallingford, Farmington, Berlin and 

 East-Haven. Also at Mount Tom in East-Hampton. {Sil- 

 liman.) Also in greenstone, Deerfield, forming geodes of 

 a light purple; crystals from one tenth of an inch to an inch 

 in diameter. Also in Westminster, Vermont, in crystals an 

 inch and an half in diameter. 



17. Ferruginous Quartz. At Litchfield. (Brace.) 



18. Fetid Quartz. I have recently found this in several 

 places, from Woodbridge, near New-Haven, to Bellows- 

 Falls in New-Hampshire, a distance of one hundred and 

 fifty miles, in loose rolled masses. In the vicinity of Con- 

 way it is very abundant, and occurs crystallized in the com- 

 mon six-sided prisms ; which are sometimes so flattened as 

 to be three times as broad as thick. In Conway it occurs 

 in veins in mica slate and granite ; less fetid, however, than 

 that which is found loose on the surface. It is traversed 

 by thin seams, or veins, apparently ferruginous; its color is 

 nearly milk white and its lustre a little resiaous. In some 

 specimens the fetid odour is very strong. 



