120 The A?nerican Geologist. February, i»99 
a considerable amount of the material. In looking around, a 
few other localities, similar to this one could detected. The 
strata of the sandstone were a few degrees inclined towards the 
bed of the creek, so that all the water, percolating through 
the porous sandstone has its natural outflow into the creek. 
Plenty of apparently pure material could be collected for 
analysis. The results of my analysis, made in the chemical 
laboratory of the Iowa State University, may be given as fol- 
lows : 
The mineral was readily soluble in cold water, leaving a 
very small residue insoluble in acids (Si O2). In boiling the 
solution, a brownish floccular precipitate separated out, prob- 
ably a basic iron salt, soluble in dilute hydrochoric acid and 
giving reaction for iron. Very small traces of alumina could 
be identified. The presence of sulphuric acid was identified 
in the ordinary way. The following is the average from two 
analyses : 
SO3 39-01 per cent. 
H.^O 32.32 per cent. 
AljOg 0.27 per cent. 
FcgOg 26.86 per cent. 
Insoluble residue SiO., 1.79 per cent. 
100.25 
Specific gravit)' was found 2.212 H = 2.5 
If the small trace of alumina is calculated as iron, there 
results the following ratio: 
SO., : Fe.,03 : H.,0 = 2.87 : I : 10.5 
or about 3 : I : lO 
corresponding to the formula Fe.2(S04)3H-iO H.^O, i. e. the 
composition of the mineral is identical with quenstedtite. 
Dana gives the following composition for quenstedtite: 
S0» 
39.83 per 
cent. 
H20 
31-35 Pt^i- 
cent. 
A1.,0., 
trace 
Fe,03 
27.66 per 
cent. 
CaO 
0.40 per 
cent. 
99-24 
The determination of the water was made by Prof. Pen- 
ticld's method and gave verv exact and identical results. 
