MINERALOGY. 41 
sediments.* Fig. 5 on Pl. 2 represents one of the most remarkable. It 
is drawn from a section of a diorite from Connecticut lake. It appears 
in the microscope as composed of a dark gray, translucent substance 
traversed by lines of greater transparency; and nothing could resemble 
more closely the structure of a coral, or of a fragment of some rhizopod. 
By reflected light the whole appears white, traversed by faintest black 
lines. Fig. 6, though less organic in appearance, is fully as remarkable 
as a decomposition product of titanic iron. It represents a form found 
abundantly in the diorite of Hanover. Persons are naturally interested 
in finding organisms in old rocks; and besides the cautionary value that 
may be attached to these figures, they are illustrative of a method of 
decomposition, which, in our greenstones, is characteristic of the titanic 
iron. 
27. SPINEL [Mg Al, O,]. 
The mineral spinel has been found in pretty little bright red octahe- 
dral crystals in a limestone rock on Saddleback mountain. 
28. MAGNETITE [Fe; Oy]. 
This ore is found in deposits of such magnitude that efforts have 
been made to mine it. It is widely distributed in smaller amounts. At 
the Franconia iron mine, in Lisbon, there is a vein from 5 to 8 feet thick 
in the gneiss rock, which was worked for some time. Fine dodecahedral 
crystals are found there. The ore is compact, fine grained, and of a 
bluish gray color. Jackson’s analysis is as follows: 
Iron proto-sesquioxide, . é F : 3 a é ‘ d 96.20 
Titanic acid, . é é F F 5 : é ‘ : ‘i 1.50 
Silica, ‘ e . . < ‘ s : ‘i * . A 2.30 
100.00 
When the vein was worked, several other minerals in fine crystallized 
condition were obtained from the mine, and it was an often-visited local- 
ity. Garnet, epidote, and hornblende were found in crystals remarkable 
for their beauty. Magnetite occurs in large beds in Unity; but in this 
* See Hawes, American Yournal of Science, iii, vol. xii, p. 134. The other gentlemen who have seen these 
specimens, and have published opinions in reference to them, are very excusable, on the ground that they saw but 
single specimens, and are not professed experts in microscopic mineralogy. The author has paid some attention 
to the subject, under competent instruction, since the paper referred to was published, 
VOL. 1. 6 
