1 26 Mineralogical Journey. 



Art. XXllI. — Mineralogical Journey in the northern parts ofJYew 

 England; by Charles Upham Shepard, Assistant to the Pro- 

 fessor of Chemistry and Mineralogy, and Lecturer on Botany in 

 Yale College. 



(Continued from Vol. XVII, p. 360.) 

 4. Precious Garnets of Hanover. 



The precious Garnets of Hanover, N. H. next invited our atten- 

 tion. This locality, from its vicinity to Dartmouth College, has long 

 been known ; and specimens from it are now common in most col- 

 lections. It is situated directly in the rear of the Medical College. 

 The gneissoid hornblende, wliich forms the gangue of the Garnet, here 

 crops out over an extent of several acres, and so abundantly, as to pre- 

 sent the aspect of an almost unbroken ledge. This rock, composed 

 principally of hornblende and quartz with occasional scales of black 

 mica, has been called greenstone : from the large proportion of horn- 

 blende it contains and its schistose structure, some geologists might 

 still be disposed to call it greenstone slate ; but its characters and con- 

 nexions appear to me, to bring it, more correctly, under gneiss. Its 

 geological disposition, is very decided and uniform ; the strata constantly 

 preserving a vertical position, and a direction varying but slightly from 

 north and south. Nearly perpendicular to its stratification, exist fre- 

 quent seams or joints ; by which, in quarrying, it separates into im- 

 perfectly rhomboidal layers or blocks, — a character no doubt depen- 

 dent upon the preponderance of hornblende in its composition. The 

 Garnets are every where dispersed through it, at distances varying 

 from immediate contact to half or three quarters of an inch apart ; 

 generally without any perceptible order, though, occasionally, follow- 

 ing the plane of stratification. 



The peculiar interest of this Garnet to the mineralogist, consists in 

 the uniform simplicity and perfection of its crystals. In size they 

 rarely exceed that of a common pea ; but their form is invariably that 

 of the dodecahedron, unmodified by the slightest replacement ; (and 

 what appeared to us as very remarkable also, considering the immense 

 quantity in which they occur,) their planes are, in every instance, 

 equally produced and perfect. Scarcely less strict is the uniformity 

 observable among them in color, transparency and lustre. 



In passing through the town of Piermoni, twenty miles north of 

 Hanover, we noticed by the road side, for a distance of several miles, 



