110 PROCEEDINGS OF THE ACADEMY OP 



The following gentlemen were elected members: 



Mr. Joseph R. Rhoads, William K. Gilbert, M. D , Mr. Samuel 

 Huston, Mr. T. Clarkson Taylor, Robert S. Kenderdine, M. D., Mr. 

 Daniel Haddock, Jr., Mr. Henry A. Dreer, Mr. Christian C. Febeger, 

 Henry Stille, M. D. 



The following were elected Correspondents : 



Rev. M. 13. Anderson, LL. D., President University of Rochester, 

 N. Y.. and Mr. Lemuel R, Carter, of Paris Hill, Oxford Co., Maine. 



On report of the respective Committees, the following papers were 

 ordered to be published : 



Notes on Some Members of the FELDSPAR Family. 

 BY ISAAC LEA. 



I have been much interested for several years past in observing and col- 

 lecting the varieties of the Feldspar Family of Chester and Delaware Counties 

 in this State. 



Finding in many places that, where the intrusive Serpentine appears, there 

 were usually to be found the finest and more vitrious varieties of Feldspar, I 

 visited all such localities, and thus have brought together, perhaps, more of 

 them than any other mineralogist who has searched in these counties. My 

 object in these researches has been solely as to their external characters, con- 

 nected with the matter which gives to them color, so far as microscopical ex- 

 amination could enable me to effect it. 



Among the numerous varieties which I have brought together, I think there 

 are three which have not been before observed. One is of a compact struc- 

 ture, almost without cleavage, and of a fine green color, approaching, as 

 regards tint, to aqua-marine, and is semi-transparent. Another, which 

 usually accompanies the first, and often passes into it, as Leelite does into 

 Feldspar, has always a definite and well characterized cleavage, the surface 

 of which presents an agreeable pearly appearance, sometimes satin-like. 

 This is usually white or grayish, sometimes inclining to a pale purplish hue, 

 particularly toward the edges of the specimens, and which seem to have been 

 enveloped in Alhite. Along those edges where the purplish hue is stronger, I 

 could, in all cases, detect small thin spangles or plates, such as constitute 

 Sunstone, Aventurine Feldspar with reddish or wine-color internal re- 

 flections. 



These reflections are minute, usually microscopic, and always, I believe, of 

 a hexagonal form or the modification of that form. 



For the green mineral, I propose the provisional name of Lennilite, having 

 found it only near the village of Lenni, in Delaware County. For the pearly 

 variety, I propose that of Delaioareite, having first found it in Delaware 

 County, among the Serpentine rocks, between Grlen Riddle and Lenni. Subse- 

 quently, I found specimens in Chester County, near to West Chester. 



The third is a variety of Feldspar which is more laminate and glassy, of a 

 dull bluish green color and semi-transparent, which has through the mass 

 usually very minute internal bright crystalline hexagonal plates giving 

 very bright reflections. This is found at Blue Hill, about two miles north of 

 Media, and is an exceedingly interesting mineral. I found a specimen very 

 similar to this, but rather more blue, some three miles southwest of West 

 Chester, which had not, however, any plates with reflections, but, with a 

 high power, numerous small, black, thin, prismatic crystals were observable. 

 For this, I propose the name of Cassinite. 



It had been known for many years that Sunstone proper existed in the 

 Homblend Rocks of Chester County, near to Kennett Square. This I found 

 in sufficient quantity and perfection to institute a good examination into the 



[May, 



