44 MINERALOGY AND LITHOLOGY. 



from the combined action of heat, resulting from metamorphic action, 

 and some reducing agent. This action has converted beds of hydrous 

 iron sesquioxide, which were accumulated by the action of water, into the 

 magnetic oxide. 



29. CiiROMiTE [Fe Cr>i O4]. 



Chromic iron has been found in several places in Vermont. In New 

 Hampshire, a small amount has been found in the soil of Dublin. It is 

 most often found associated with serpentine rocks, of which we have 

 none that is readily accessible. 



30. Chrysoberyl [Be AI2 O4]. 



This rare mineral has been found in a narrow vein, which was opened 

 in making the deep cut through the granite recks at Orange summit.* 

 The form of the crystals was compound, like that of the crystals from 

 Haddam in Connecticut, which are well known ; but none were found 

 with terminal planes to the crystals, and all were more or less imperfect, 



31. Cassiterite [Sll O2]. 



Dr. Jackson, thinking that circumstances were favorable for the discov- 

 ery of tin mines, made a most careful search for this mineral in our state, 

 and at last succeeded in finding it ; since which discovery much time and 

 money have been expended in the hope of turning the discovery to prac- 

 tical advantage, but thus far with no success. 



It was first discovered in 1841, in the town of Jackson. It occurs in 

 little veins at the junction of a dyke with the schistose rocks. Large 

 excavations have been made with the idea in view of extracting the ore, 

 but no quantities sufficient to yield metal of consequence were met with. 

 This was the first discovery of tin ore in the United States. 



Cassiterite, as found at Jackson, is sometimes crystalline and sometimes 

 massive. Fig. 6 on PI. 3 represents one of the crystals. The figure was 

 drawn by Mr. J. E. Teschemacher for Dr. Jackson. It is a twin crystal, 

 the twinning plane being parallel to the plane of a pyramid of the second 

 order. It is much enlarged, for the best crystals are very small. I have 

 seen no perfect crystals from there ; but those that I have found appear 



* Prof. O. P. Hubbard, American jTournai p/ Science, \\, vol. xi, p. 424. 



