120 PROCEEDINGS OF THE ACADEMY OF 



to the primatic hexagon sides of Corundum. Both sets of these crystals ar« 

 enlarged to about 200 diameters, for the purpose of giving distinctly their very 

 singular form. 



Specimens of Oarnet examined from all localities obtainable, presented very 

 different aspects. When crystals were found in them they always proved to 

 be acicular in form, but by no means similarly regular or of the same length, 

 direction, or of the same size. 



Fig. 3. A Bohemian cut GarTiei presented three sets of numerous, thickly set, 

 parallel, acicular crystals, which crossed at an angle of 120°, forming a very 

 regular lattice-work appearance. 



Fig. 4. A Bohemian cut Garnet presented only two sets of acicular crystals, 

 which were usually at right angles, but some were inclined from perpendicu- 

 larity and they Avere not so long as those of figure 3. 



Fig. 5. A Bohemian cut Garnet presented a very different set of crystals. 

 They were generally short, comparatively, and pointed in every possible direc- 

 tion. 



Fig. 6. Garnet from Ceylon — Cinnamon-stone — fractured portions, not cut and 

 polished. The acicular crystals were much shorter, rather thicker and much 

 more bluntly terminated than in Fig. 5. They are placed at all angles. Ten 

 specimens only in 80 examined had any thing like crystals, while all had 

 irregular rifts or cavities within. 



Fig. 7. Precious Garnet = Pyroju? from Green'.s Mill, Delaware Co., Penn., 

 presented acicular crystals somewhat like Bohemian Garnet, fig. 3, but the 

 three sets, while they take the same three directions, are shorter and left in- 

 terspaces as shown in the figure. 



Fig. 8. Garnet from North Carolina. A thin fracture from a compact garnet 

 of large size, perhaps two inches in diameter. The acicular crystals are not 

 very numerous — they are thin and not continuous. Connected with these are 

 a few dark crystals. These take no particular direction like the others, but 

 seem to be interspersed throughout. 



Fig. 9. Labradorite. This specimen is a small polished one from Ceylon, 

 and belongs to Dr. Ruschenberger. Besides the usual play of pavonine colors 

 in Labradorite, I have found in all the specimens! have examined from various 

 other localities, very minute reflecting crystals like those in Sunstone, and 

 which are no doubt the same, but differing in size, being smaller so far as I have 

 observed. The microscopic forms as figured will be observed to consist of two 

 sets apparently distinct. The larger are rather irregular and black. The thinner 

 are rather shorter and more delicate. These are not the reflection of the plates 

 of Got/lite,* they aie the black crystals which are usually in dark Feldspar. 



Fig. 10. Black Feldspar. A small specimen of black Feldspar, translucent 

 in thin pieces, from Chester Co., Penn., presented quite a different appearance 

 from Labradorite in its minute, black included crystals. They are very numer- 

 ous, very short, opake black, and irregular in form. They are closely set and 

 irregular in their direction. There were no reflections from any of these in- 

 cluded crystals. 



Fig. 11. Barite, fvom Antwerp, Jefferson Co., New York, a represents some 

 opake crystals observed in a small prismatic crystal. They cannot be, I think, 

 rifts, and yet they are evidently without planes, b represents singular impres- 

 sions on the surface of one of the prismatic planes, and their singular form, 

 like the common horse-shoe magnet, induces me to call attention to them. 



Fig. 12. Amethyst. A specimen from Thunder Baj-, Lake Superior, presents 

 very remarkable globules, some of an orange-yellow and some of a dark- 

 green. These are very visible to the naked eye, and in the figure they are not 



* The plates of Giitliite when held at a proper angle may easily be seen by the naked 

 eye. 



[May, 



