76 MINERALOGY AND LITHOLOGY. 
quartz. Some of these little crystals exist in the sienite at Sandwich, 
and are there very perfect in form. 
49. VESUVIANITE (IpocrasE) [Cag Al, Si, Ong]. 
Large and fine crystals of vesuvianite have been found at Amherst, 
and also at Warren. These crystals occur on the surfaces of contact of 
the limestones and siliceous schists that are there associated. One of 
the crystals from Amherst is represented in Fig. 2 on Pl.3. It is taken 
from the second edition of Dana’s Mineralogy. 
e 
50. Eprpote [H? Ca‘ (Al, Fe”)? Si® O*]. 
We have epidote both in isolated crystals and in our rocks. It is 
found at Lisbon in light yellow acicular crystals, and in larger, finer forms. 
Very pretty twin crystals, and also a massive variety, are found there. It 
occurs at Warren, associated with quartz and pyrites. It fills a vein in 
Jackson, from which immense crystals have been taken, some of which 
were eight inches in diameter and of a fine green color (Jackson). Smaller 
but better crystals, and also twins, are more common. It is found at 
Bedford, Gilmanton, Hanover, Portsmouth (radiated acicular crystals in 
hornblende), Exeter (very beautiful groups of radiating crystals), and 
Benton (in boulders). 
As a rock constituent, epidote is preéminently characteristic as a 
decomposition product in certain basic rocks. It is found in seams and 
cracks in the metamorphic diorites that are so common in the Connecti- 
cut valley, and is an almost constant microscopic ingredient of the rocks 
themselves. The same is true of some of our eruptive rocks. In micro- 
scopic sections it is trichroic; but the colors are often so faint as to 
render the recognition of this difficult. It may be said, however, that it 
is usually yellow in color, and, when revolved between crossed Nicols, the 
colors obtained are perhaps more brilliant than those shown by any other 
mineral. 
Where the rocks contain the most basic feldspars, and where this feld- 
spar is dull by decomposition, there epidote is most often found. In our 
light green feldspathic diorites, epidote seems to be the mineral most 
commonly found in and about the triclinic feldspar as a product of its 
decay. At times, this process of alteration has proceeded so far that 
