72 MINERALOGY AND LITHOLOGY. 



large masses, which are destitute of any crystalline form. We possess 

 quite a variety of garnets, the prominent varieties being the red iron 

 alumina garnet called almandite; the manganese iron alumina garnet 

 called spessartite ; the lime alumina garnet called cinnamon garnet or 

 grossularite; and the lime iron garnet called andradite. 



The red almandine garnet is common in the hornblendic rocks of the 

 Connecticut valley, and also in the gneiss and mica schists all over the 

 state. Sometimes, as at Hanover, the crystals are nearly clear, and 

 resemble the stones from which the gems are cut, but more commonly 

 they are only translucent. They vary in size from microscopic grains to 

 crystals an inch in diameter. They are commonly dodecahedral, though 

 the edges are often replaced by small planes of the trapezohedron. They 

 are found in the most perfect forms in chlorite rocks ; but small and very 

 perfect crystals are found in the greatest profusion in some of the horn- 

 blende rocks. This variety of garnet is found in a chlorite rock at Haver- 

 hill, in large crystals li inches in diameter. Newington, Lisbon, Unity, 

 Orford, Dorchester, Dalton, and Windham are localities for it, and it is 

 common in some of the mica schists and granitic rocks of the moun- 

 tains, though the crystals are not so often perfect. Sometimes fine crys- 

 tals are dug from the soil where they have been deposited after the disin- 

 tegration of the rocks ; and from this source the finest pieces for cutting 

 have been obtained. This variety of garnet is common in the great 

 granite veins like those at Acworth and Grafton. Clear and beautiful 

 little crystals, and large imperfect ones, are abundant. Very large and 

 perfect crystals have been found in the granite veins at Winchester. 

 They are trapezohedral in form, but have the planes of the rhombic 

 dodecahedron. 



Spessartite — the silicate of manganese, iron, and alumina — is most 

 common in the mica schist rocks. Its crystals are usually larger. It 

 commonly crystallizes in trapezohedrons, though the planes of the dodec- 

 ahedron are often seen. A great many of them have been obtained by 

 mineralogists from the mica schist at Springfield, where they are very 

 abundant, and very perfect in their crystallization. 



Andradite — the lime iron garnet — is very dark in its color, being deep 

 blood-red, and often nearly black. It has been identified by W. Fisher * 



* American Journal of Science, ii, vol, ix, p. 84. 



