108 MINERALOGY AND LITHOLOGY. 
67. CyaniTE [Al, Si O5]. 
The ordinary blue, bladed crystals of this mineral abound in many 
localities in our state. They are conspicuous, and easily recognized. 
These blades are made by the meeting of prismatic planes, which make 
an angle with one another of 106°, and which are also the cleavage 
planes; hence, in thin sections of the rocks, cyanite, when cut parallel to 
the base, appears as composed of many little rhombs. In thin sections it 
can easily be recognized as triclinic, since none of its sections are dark 
when the prism is parallel with the plane of a Nicol. This can also be 
tried with cleavage bits, that are so easily obtained ; but it is to be noted, 
that unless they are very thin, no result is obtained, since the large crys- 
tals are so often composed of little crystals in twinned positions that the 
splinters, if not very thin, are always colored when revolved between the 
Nicol prisms. Bellows Falls, Lyme (in the north-west part), Jaffrey (Mt. 
Monadnock), Orford, Warren, Hanover, and Norwich, Vt. are places 
where good specimens of cyanite can be obtained. 
68. TITANITE (SPHENE) [Ca Ti Si O°]. 
This is not of much mineralogical interest, save as a rock constituent, 
in which condition it is widely distributed, though rarely visible except 
with the microscope. It commonly presents itself in rounded grains, but 
sometimes the rhombic and six- or eight-sided forms, which are obtained 
by cutting its common crystals, are seen. The sections are usually 
greenish-yellow and dichroic, but, owing to the faintness of its color in 
thin sections, it is not always possible to observe this. In color and 
dichroism it looks like epidote, from which it is easily distinguished, 
because, between crossed Nicols it gives scarcely any colors, while epi- 
dote gives very brilliant interference colors. 
In our rocks titanite appears usually to be a product resulting from 
the decomposition of titanic iron. For example: it has been explained 
that the titanic iron in our greenstones is often subjected to a peculiar 
kind of decomposition. Now, where the skeletons of titanic iron are 
most abundant, there the sphene is found in the largest amounts. As 
was stated, the iron of titanic iron being removed, the product remaining 
has been shown by Prof. Lasaulx to be titanate of lime, but, if silica takes 
