112 RE-EXAMINATION OF AMERICAN MINERALS. 



~No. 1 was from a specimen in our own collection. No. 2 

 was from the original specimen in Prof. Silliman's cabinet. 

 Nos. 3 and 4 were specimens received from Messrs. Willrams 

 and Jeffries, of Westchester, Pa. Specific gravity Nos. 1 and 

 2, 2.83. The analyses give the formula ft Si+& 3 Si 2 +2H. 



Atoms. At. weight. Per cent. Oxygen ratio. 



Silica 3 1731.93 39.63 9 



Alumina 3 1925.40 44.05 9 



Soda \ 193.60 4.43 \ - 



Potash | 394.42 6.74/ 



Water 2 225.00 5.15 2 



This mineral in its most beautiful form is of rare occurrence 

 (analyses 1 and 2 are of this variety); there is, however, an- 

 other variety, not differing essentially in physical characters 

 or in chemical composition, which is found in considerable 

 abundance at the locality. 



In all probability the mineral alluded to as Muscovite (?) in 

 the memoir on the minerals associated with emery* is this 

 mineral; and when we are able to get at certain specimens 

 from Asia Minor, containing this mica in a pure state, this 

 point will be investigated. It is of much interest toward 

 tracing out its geological connection with corundum forma- 

 tions widely separated, in which respect it may resemble 



emerylite. 



3. Mica from Litchfield, Conn. 



This mineral is associated with the kyanite of Litchfield. 

 In general appearance it resembles margarodite. Hardness= 

 3.35; specific gravity 2.76 ; almost colorless, having a faint 

 tinge of green ; transparent ; luster pearly. The results of 

 two analyses gave 



Si XI 3Fe Mg Ca Mn Na K El H 



1. 44.60 36.23 1.34 0.37 0.50 trace 4.10 6.20 trace 5.26 



2. 44.50 37.10 undet. undet 4.00 5.90 5.16 



These correspond very closely with Liebnerite, as well as 



with Damourite and some analyses of margarodite. Annexed 

 are the analyses for comparison : 



Si £1 Fe Mn Mg K Na fl 



Liebnerite.... 44.66 36.51 1.75 1.40 9.90 0.92 4.49 Marignac. 



£e 



Damourite... 45.22 37.87 trace 11.20 5.25 Delesse. 



Margarodite. 46.23 33.08 3.48 trace 2.10 8.87 1.45 4.12 Delesse. 



* Amer. Jour. Science and Arts, 2d series, xi, 62. 



