210 Reéxamination 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. Williams and Jeffries 
of Westchester, Pa. Sp. Gr. No. 1 and 2, 2:83. The analyses 
give the formula, 8 Si+Rs Si2+oH. 
‘ 
toms. At. weight. Per ct. Oxygen ratio. 
Silica, 3 1731°93 39: 
Alumina, 3 1925-40 44:05 9 
Soda, 193°60 4:43 ‘ 1 
Potash, 5 394-42 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, another 
variety, not differing essentially in physical characters, or 12 
chemical composition, which is found in considerable abundance 
at the locality. ; 
In all probability the mineral alluded to as Muscovite? 1n the 
memoir on the minerals associated with emery* is this mineral; 
and when we may be able to get at certain specimens from Asi@ 
Minor, containing this mica in a pure state, this point will be 
investigated. It is of much interest towards tracing out its ge 
ogical connection with corundum formations widely separated, 
d 
in which respect it may resemble emerylite. 
3. Mica from Litchfield, Conn. 
This mineral is associated with the Kyanite of Litchfield. cS 
Hard 
general appearance it resembles margarodite. ardness = 9%) 
Sp. Gr. 2:76. Almost colorless, having a faint tinge of green. 
Transparent. Lustre pearly. The results of two analyses g2¥° 
Si A Meo: Os Mv Nei Ke Heo 
1. 4460 3623 134 037 050 trace 410 620 , War “~ 
2 4450 7-10 undet. undet. #00 50 OO 
‘These correspond very closely with Liebnerite, as well 3s 
with Damourite, and some analyses of margarodite. Annexed 
are the analyses for comparison : 
; Si Al Fe Mn Mg KK. Na Ht Marigns. 
Liebnerite, 4466 3651 175 —— 140 990 092 #49 =m 
Damourite, 45°22 87°87 trace —— —— 1120 —— pps v8 
Margarodite, 4623 3308 348 trace 210 887 145 #12 
. a . + i : ut 
_ The silica and peroxydst in these analyses are identical, » to 
in common with many of the micas, it is extremely difficut of 
deduce any one formula that would be a correct expressio? 
* This Journal, [2], xi, 62. 
¢ Conchdeding the itera: Ribiasibtceien jusceeyt 
