312 Scientific Notices — Mineralogy. [Oct. 



am aware that writers on crystallography do not admit the 

 existence of re-entering angles in single crystals ; but I must 

 own my inability to detect any signs of those which I speak of 

 being double. 



" There are also some instances of peculiarity in the forms of 

 summits which it may be worth while to notice. I can think of 

 no better way to give a just notion of that to which I refer than 

 the following : — Suppose a person to be forming a crystal by 

 placing laminae of the proper form upon each other, till ho had 

 commenced forming the summit by laminae of smaller dimen- 

 sions; but after the summit was partially formed should deter- 

 mine to carry the crystal higher in a form similar to the lower 

 part, and after having done so for perhaps half an inch, should 

 then finish with a summit. In some cases the appearance is as 

 if this process had been repeated the second time before the last 

 summit was formed. The partial summits are sometimes like 

 the ultimate ones, sometimes unlike. It is impossible, however, 

 within the limits of this paper, to notice all the interesting 

 appearances exhibited on these crystals. Of themselves, they 

 might form a copious volume for the crystallographer to study." 

 — (American Journal of Science.) 



11. American Localities of certain Minerals and Fossils. 

 A new variety of quartz has been found in Chester, Massa- 

 chusetts, by Dr. Emmons. It is distinctly laminated, the folia 

 separate by a blow, like those of laminated calcareous spar. It 

 is partially translucent, though the faces of the laminae have not 

 a perfect crystalline smoothness, and are marked with oblique 



striae. 



Prismatic mica occurs in Chester, in fine filaments, which 

 gradually pass into rhombic prisms. It is abundant and beauti- 

 ful. The fibres are often " as delicate as those of amianthus." 



Citmmingtonite. — Prof. Dewey has given this name to a 

 variety of epidote, found at Cumro>-"~lon, Massachusetts. "Its 

 colour is grey, sometimes with a taint reddish tinge, unless when 

 acted on by the weather, when its colour is yellowish. It is in 

 indistinct prisms, with oblique seams like zoisite, and in 

 radiated or fascicled masses, which are composed of slender 

 prisms. Lustre somewhat shining or pearly. It is nearly as 

 hard as quartz, and sometimes makes a slight impression upon 

 rock crystal. Before the blowpipe it blackens, and a small 

 portion melts, when the heat is very great, into a black slag, 

 which is attracted by the magnet. Its point of fusion seems to 

 be about that of zoisite. After allowing for some absorption, the 

 specific gravity may be taken as about 3-42. It is so peculiar a 

 mineral, that it deserves, even as a variety, a particular name. 



" With quartz and garnet, it forms a large mass in Cumming- 

 ton. The cavities in the rock contain pulverulent sulphur of a 



