66 G. J. Brush’s Mineralogical Notices. 
by heating in a glass tube in a stream of dry air and collecting 
the moisture in a chlorid of calcium tube, and in the two other 
analyses the loss by ignition was considered as water after sub- 
tracting from it the small amount of carbonic acid which the 
mineral was found to contain. The following are the results: 
The material for analyses Nos. 1, 2 and 3 was taken from three 
crystals differing considerably in external characters: No.1, un- 
cleavable; No. 2, distinctly cleavable; No. 3, mixed cleavable 
and uncleavable. Nos. 4 and 5 are two determinations made on 
No. 3 to ascertain the state of oxydation of the iron. 
275 2736 
Sp. gr., : “749 
- 2. 3. 4, 5. 
+ Silica, 45°55 45°75 45-70 
: Alumina, oe 31°62 31°25 31°65 ‘ ‘ . 
Sesquioxyd of iron, ee ae — 9 2 
Protoxyd of iron, 088 1:05 110 72 81 
Lime, 2°42 1:96 2°21 
Magnesia, 3°38 3°59 3°46 
So 1:06 0°67 0:90 
Potash, 811 8-47 8:06 
Water, : 7-32 6°58 TO1 
Carbonate of lime, 0°56 —_— 
4 
This uniformity of composition was unexpected, and is quite 
remarkable. The a che given clearly shows that the crys- 
tals are pseudomorphs. This appears (1.) from the wide variation 
in angle; for such variations, while hardly known in real erys- 
tals that are apparently so perfect in their faces, do exist in 
here altered is a question more difficult to answer. One fact is 
well as the form, that the 
crystallization is hexagonal and not trimetric. 
tees as well as chemical characters this substance ap- 
es gieseckite, liebenerite and pinite, all of which have 
considered as pseudomorphous minerals. In the recent 
of gieseckite by v. Hauer he obtained :— 
ee oe oe aoe it 
(4640 «2660 6:30 tr. 835 4846 716==99°25 
4536 89 2717 739 —— 687 
— 
given as protoxyd, but no direct deter- 
Was made to ascertain the state of oxydation. If it be 
d as sesquioxyd, and reco the oxygen ratio with 
1 in No. 1 was 
was made to a 
