298 SS. L. Penfield—Chemical Composition of Amblygonite. 
For more easy comparison the ratios from the above analyses 
I 
are collected in the following table by themselves, where R 
a. 
equa I 
P Al R  (O8,F) 
i Penig, Saxony 1°00 "96 "98 1°16 
Ii. Montebras, France, A 1°00 97 98 1:17 
Ill. Auburn, Maine 00 96 97 1°06 
IV. Hebron, Maine, A 1:00 97 95 1°13 
Paris, e 1°00 96 97 147% 
VI. Hebron, Maine,B 1:00 98 ‘95 1°27 
VIL. Branchville, Conn. 1:00 "97 "96 1°09 
VIIL Montebras, France, B 1:00 96 "96 1°21 
It will be seen that all of these approach closely to the ratio 
: rit 1, hence I propose the formula Al,P,O,+2R (OH, F) — 
ae + oR On, Fe as the true formula for all 
oe hes 
varieties of this mineral. 
(hebronite of von Kobell), including analyses II to v. 
above. The mineral from Branchville has not been examined 
t will be seen in comparing the above ratios that in every 
case the ratio of P to (OH, F) is in excess of that of the Al te 
R. Two theories suggest themselves to account for this, the 
first of which seems the most plausible. First: most miner 
which are ordinaril counties. as anhydrous contain a § 
amount of water, which is not calculated in the ratios, i? 
8, a 
that when added to the Al and R it will make the ratio w! 
equal 1:1: 1, then the ratio of (OH, F) will be: Penig; 
