78 MINERALOGY AND LITHOLOGY. 
These analyses agree closely with the formula given. The iolite is 
usually found in large, flat pieces, with no crystalline planes except the 
base. Crystals with prismatic faces are not rare, but they are commonly 
much decomposed. 
53. CHLOROPHYLLITE. 
Tolite, as already stated, is a mineral that is very easily altered, and 
many of its decomposition products have been analyzed, and given dis- 
tinctive names. When Dr. Jackson made his geological survey of this 
state, he discovered at Unity (where iolite, also, is found) a hydrated 
silicate, to which, on analysis, he gave the name of chlorophyllite. This 
substance was also analyzed by Rammelsberg, who places it along with 
several other like substances in a supplement to iolite. Dana classes 
all these substances together under the name of fahlunite, a species 
belonging with the hydrous silicates. The following are the analyses of 
chlorophyllite from Unity: 
Jackson,* Rammelsberg.t 
Silica, . ‘ , . i ‘ ‘ 5 ‘ 45.20 46.31 
Alumina, . a ; : . i ; . 27.60 25.17 
Iron sesquioxide, . : : z 5 . ; 9-17 10.99 
Manganese protoxide, . . 5 : 5 ‘ 4.08 tr: 
Magnesia, ; F : : : 5 . : 9.60 10.91 
Lime, . J - . . ‘ j ‘ ey Gaseesueys 58 
Water, . a Fi : ‘ 2 : . . 3.60 6.70 
99.25 100.66 
Rammelsberg remarks that his analysis gives, on calculation, a quantiva- 
lent ratio, which is that of a definite hydrate of the species iolite, or a 
species with the same formula as iolite, plus three or four molecules 
of water. As Jackson's analysis, when compared with Rammelsberg’s, 
shows wide variations, chlorophyllite must be regarded as a product 
resulting from the decomposition of iolite. 
Mica. 
Mica in our state is an important mineral from an economic stand- 
point, and a very interesting mineral from a scientific. We have some 
* Rep. Geol. N. H., 1844. + Rammelsberg’s Min. Chem., 1875, p. 653. 
