XI] GRANITES AND GRANITIC VEIN-STONES. 201 



25. The veins which we have described are frequently of 

 very limited extent, and seem to occupy short and irregular 

 fissures, while in. other cases the mineral aggregates which 

 characterize them occur in nests or geodes. This is seen near 

 Fall Brook, in the Nerepis valley, in New Brunswick, where 

 the red micaceous granite is in one part very friable, and pre- 

 sents irregular geode-like cavities, sometimes several inches in 

 diameter, which are" partially filled by radiating prisms of 

 black tourmaline, accompanied with quartz and albite crystals, 

 and more rarely small octahedrons of purple fluorite. The en- 

 closing granite is composed of deep red orthoclase, with small 

 portions of a white triclinic feldspar, smoky quartz, and black 

 mica. The conditions seen at this place recall the description 

 of the famous locality of feldspars, etc., at Fariolo, near Baveno, 

 in northern Italy. The rock of that place, described as a 

 granite, resembles, in a specimen before me, some of the intru- 

 sive granites of New Brunswick, and contains a pink and a 

 white feldspar, with a little black mica. It includes veins of 

 graphic granite, and also spheroidal masses, which differ in tex- 

 ture from the mass of the rock, and present geodes of consider- 

 able size, lined with fine large red and white crystals of ortho- 

 clase, accompanied by albite, epidote, quartz, fluorite, and a 

 greenish mica (or chlorite), all of which, according to Fournet, 

 are so mingled and interlocked as to show that they are of con- 

 temporaneous origin. To these are to be added, as occurring 

 in the geodes, prehnite, calcite, hyalite, and specular iron. The 

 orthoclase crystals often have adhering to their opposite faces 

 crystalline plates of albite, which are larger than the planes to 

 which they are attached. The crystals of orthoclase, moreover, 

 frequently present hollowed-out or hopper-shaped faces, which 

 Fournet happily describes as resulting from the forming of the 

 framework or skeleton of the crystals, when the material was 

 not sufficient for their completion. A process analogous to this 

 is often seen in crystallization, whether from fusion, solution, 

 or vaporous condensation, giving rise in some cases to external 

 depressions, and in others to internal cavities in the resulting 

 crystals. Fournet ascribes the formation of the geodes in the 

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