42 MINERALOGY AND LITHOLOGY. 
ore there is a considerable percentage of titanic acid. Large amounts 
of magnetite are associated with the hematite at Bartlett. At Swanzey 
large crystalline masses are found in a granite vein. In Amherst, fine 
crystals having the planes of a cube and octahedron occur; and rhombic 
dodecahedral crystals are also found. The crystals at this place are 
sometimes two inches in diameter. At Winchester there is a large vein 
that was once worked ; it is contaminated with pyrites. Other localities 
are Berlin, Piermont, Jackson (on Thorn mountain), Lebanon, Benton, 
and Easton, besides many smaller deposits unnecessary to mention. 
There are, moreover, many localities in the state, on approaching which 
the magnetic needle is very strongly deflected; and the presence of large 
bodies of ore is suspected but not proved. 
Native lodestones are found on Gunstock mountain in Gilford. 
Magnetite is one of the most commonly occurring minerals in rocks of 
all kinds, and offers some interesting features for microscopic study. In 
almost all our rocks it is present either as an essential or an accessory 
ingredient. Even in the thinnest sections of the rocks it is perfectly 
opaque, but it is evident that, could it be made thin enough, it would be 
translucent, since in our mica quarries at Alstead it has been found in 
such thin films, between the layers of mica, as to be plainly transparent. 
These films have been shown by Prof. Brush to be magnetite.* When 
the light from below the stage is shut off, the surface of a section of 
magnetite has a bluish metallic lustre by reflected light. As a con- 
stituent of the rocks, it is often in wholly irregular grains, and, again, it 
is often in minute crystals of perfect form. In our trap rocks it is quite 
generally crystallized ; and the little crystals are often grouped together 
in various ways, sometimes forming quite complicated figures. The 
magnetite in sections of these rocks is seen in little squares or triangles, 
which are sections of octahedrons; and in more complicated right-angled 
forms, which result from the compounding of its isometric crystals. On 
Pl. 2 are represented some of the groups of crystals as seen in the rocks. 
Figs. 4 and 4@ are from a section of the diabase at Bemis brook; 44 and 
4c, from the same rock at the Lincoln Flume; and 4d is a more delicate 
form, which is drawn from a section of the porphyritic diabase of Con- 
* See Dana’s Mineralogy, p. 150. 
+ See Pl. iii, in Zrkel’s Basaltgesteine. 
