488 Whitney's Description and Analysis of 
of phosphorus, a glass enclosing a siliceous skeleton and 
faintly tinged by iron. 
The analysis of the ignited mineral gave 
Oxygen. Ratio. . Calculated. 
Silica 46.12 23.96 3 46.17 
Alumina anda little Fe 25.91 12.09 ji 25.68 
Lime 21.03 l i 
8.14 
Soda 85 7.90 1 2 z 
99.91 
The oxygen of the silica, alumina and lime being as 
3: 12:1, or 6 : 3 : 2, the formula will be 
Ge Bi 4- dd Si 
This, it will be perceived, is the formula which is given by 
Walmstedt for Prehnite, except that it contains no water. 
The Jacksonite, dried at 100° C., was found to contain less 
than 35 per cent. of water. The ratio of the oxygen in this 
mineral is an unusual one, and had led Berzelius to adopt 
another formula for Prehnite. 
oP is se HL. CHLORASTROLITE. 
This mineral was found by Dr. C. T. Jackson on the shores 
of Isle Royale, in small rounded pebbles. It occurs in finely 
radiated, stellated masses, with a pearly lustre, and slightly 
chatoyant on the rounded sides. Hardness 5.5 to 6.; Spe 
cific gravity 3.180; color light bluish green. 
In the open tube it gives water and becomes white. 
Before the blowpipe it fuses with great facility to a greyish, 
blebby glass. It intumesces and swells up like a zeolite. 
Soda dissolves it in small quantity and gives a bead colored 
by a trace of manganese; if more of the assay be added 1t 
swells up to an infusible slag. ] = 
It is dissolved by borax readily, and in considerable quantity, 
to a transparent glass colored by iron. - 
i of phosphorus dissolves it in small quantity and give 
reaction of iron. 
