MINERALOGY. 25 



5. Arsenic. 



Though ores of arsenic are common, native arsenic is a rare mineral 

 in the United States, and almost its only localities are in New Hamp- 

 shire. It has been observed by Jackson on the estate of Francis Kim- 

 ball, in the town of Haverhill, and also at the tin mine in Jackson. In 

 both these places it occurs in thin layers in a dark blue mica schist, asso- 

 ciated with iron and arsenical pyrites. 



Native arsenic is volatile at a low temperature, and, when volatilized, 

 gives forth its disagreeable but characteristic ordor of garlic. Dr. Jack- 

 son, in describing its occurrence at Haverhill, states that on hot days 

 it is somewhat volatilized by the heat of the sun striking upon the rocks 

 where it is found, so that on such days the odor of arsenic is perceptible 

 when one is near the locality. The garlic odor is evolved when the ore 

 is struck with the hammer ; but other arsenic minerals are like it in this 

 respect. 



6. Sulphur. 



Native sulphur occurs sparingly in some places, and results from the 

 decomposition of iron pyrites. Pyrites, by exposure, is oxidized to iron 

 sulphate, and this process is sometimes attended by the separation of sul- 

 phur. It is in connection with pyrite and sulphate of iron that it is 

 found. Thus associated, it has been observed in the iron ore beds at 

 Brentwood. It has also been found in Chester in small quantities in a 

 bed of tremolite, into which position it was probably conveyed by a pro- 

 cess of sublimation. 



7. Graphite. 



Graphite or plumbago is widely distributed through our rocks, as it is 

 all over New England. Sometimes it forms large deposits ; and some- 

 times, in the form of scales, it is an ingredient of the rocks, at times 

 forming a considerable proportion of their composition, and at times a 

 mere microscopic impurity. In the towns of Nelson and Goshen it has 

 been mined, although the quality is not of the best. 



Large specimens are found at Bristol. In Chester, it is found in veins 

 in the mica slate. On the north side of Monadnock mountain, nodules 

 with a coarse texture are found. At Sutton much is found, and of good 



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