MINERALOGY. I3I 



cavities which were represented in Fig. 3 on PI. 6 to show the analcite, 

 were all first coated with sphaerosiderite, which often assumed in them 

 the most fantastic forms. In the thin sections it is deep yellow in color, 

 appears often agate-like in structure, but in polarized light appears to be 

 an aggregate of very fine fibres or scales. It is not uncommon to find 

 some of this substance in sections of our basic rocks. 



93. RlIODOCHROSITE [Mn CO^]. 



This mineral is found at Winchester. When pure, it has a light rose 

 color ; but our mineral is usually blackened by decomposition. It is not 

 common, and does not show its crystalline form, which is rhombohedral. 



94. Malachite [Cu^ CO' + H^O]. 



This bright green carbonate of copper, though not found in well crys- 

 tallized forms, occurs at Littleton in the slaty rocks, in stellated groups 

 of needle-like crystals. In the condition of a green crust it has been 

 found in the rocks at Franconia, Hanover, Dalton, and Orford. It is 

 associated with sulphurets of copper, and generally results from their 

 decomposition. 



95. AZURITE [Cu=' C O' + H^O]. 



The blue carbonate of copper is associated with the green at Fran- 

 conia. Like the malachite, it is in the condition of a non-crystalline 

 earthy crust. 



********* 



In concluding this chapter, what has been said with reference to the 

 localities of minerals may be very conveniently summed up in a cata- 

 logue of the towns, and the minerals that, to the knowledge of the sur- 

 vey, have been there identified. This catalogue not only embraces those 

 mineral occurrences that have been referred to in the preceding pages, 

 but also includes many others which in those connections it would have 

 been tedious to enumerate, and mention of which is more serviceable 

 when placed here. Though many of these minerals have been known 

 to exist for a century, still to the field laborers on this survey, with Prof. 

 Hitchcock at their head, the people are indebted for a knowledge of a 

 larsfe number of these occurrences. 



