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. CHROMITE [Fe Cr, O,]. 
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. CurysoBeryL [Be Al, O,]. 
This rare mineral has been found in a narrow vein, which was opened 
in making the deep cut through the granite rocks 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. CassIrERITE [Sn OJ]. 
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 Pl. 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 Yournal of Science, ii, vol. xi, p. 424. 
