50 ECONOMIC GEOLOGY, 



is Strafford, Vt, where copperas has been manufactured for the past fifty 

 years. From that single locality on Copperas hill, thousands of tons of 

 ore have been sent to market. The species is pyrrhotite, containing 39.5 

 per cent, of sulphur, and is therefore less valuable than common pyrites, 

 which has 53.3 per cent, of sulphur. 



There are several veins of pyrites in New Hampshire that can be 

 successfully mined for the manufacturing establishments, especially as 

 copper is usually associated with them. These veins are also nearer the 

 market than those of Vermont, which are now mined so largely. Perhaps 

 the most important of these is in the south-west part of Croydon. This 

 has been visited twice, — in June, 1869, and May, 1870. The results of 

 our examination are briefly these : The rock is micaceous and gneissic, 

 one of the sub-divisions of the White Mountain series probably. It is 

 elevated two or three hundred feet, on the south-east flank of Croydon 

 mountain. Higher up is the quartzite, dipping at a high angle to N. 65° 

 W, It probably overlies the sulphuret schist unconformably, as it cer- 

 tainly does three miles farther north, the latter dipping 80° W, 10° S. 

 One or two hundred feet east of the vein is a white gneissic rock, carry- 

 ing an unusual amount of mica. This is parallel with it, and may be 

 used as a guide in tracing it through the country. In this way the vein 

 was followed for three fourths of a mile to the north, and from what was 

 said to us, it is judged to extend equally far to the south. The vein has 

 been opened to the depth of twenty-five feet. It was full of water at our 

 first visit, but was drained at the second visit by means of a syphon. 

 The vein mass is uniform in its width and composition. Next the hang- 

 ing wall is six inches width of slaty layers, holding both copper and iron 

 pyrites. Next succeeds two feet thickness of magnetic pyrites, or pyr- 

 rhotite, very compact, solid, and nearly pure. There is no foreign min- 

 eral present except small nodules of quartz. Next follows one foot ten 

 inches of the same, less compact. Fourthly, is two feet thickness of 

 gangue of quartz, or a micaceous mass carrying a large proportion of 

 copper pyrites and zincblende. Below all this is a slaty mass three or 

 four feet in thickness, similar to the upper layer, carrying considerable 

 pyrites, which possibly may be utilized. The second, third, and fourth 

 of these layers are valuable, and united amount to six feet in thickness. 

 By Prof, Seely's determination, the sulphur in No, 2 amounts to 37.68 



