284 
ANALYSES OF ROCKS, TJ. S. GEOLOGICAL SURVEY. [no. 228. 
9. BLUFF, FAYETTE COUNTY, TEXAS. 
Analyzed by J. E. Whitfield, record No. 824, and described in Bull. 
60, p. 107. Sp. gv. , 3.510. Examined microscopically by G. P. Merrill, 
who reports, in addition to nickel-iron and pyrrhotite, olivine, ensta- 
tite, and what appears to be augite or an allied pyroxene. See Amer. 
Journ. Sci., 3d series, vol. 36, August, 1888. 
A. Total analysis. 
B. Nickel-iron (5.67 per cent of total). 
C. Part soluble in hydrochloric acid, calculated to 100 per cent 
(60.62 per cent of total). 
D. Insoluble part, calculated to 100 per cent (33.3 per cent of total). 
A. 
B. 
c. 
D. 
Si0 2 
37. 70 
2.17 
23.82 
4.41 
1.59 
.88 
.16 
.37 
.45 
2.20 
25. 94 
.25 
1.30 
82.42 
15.44 
2.14 
33. 59 
1.34 
31.12 
49.64 
A1 2 3 
4.12 
FeO 
15. 56 
Fe 
NiO 
2.66 
trace 
Ni 
CoO 
.27 
trace 
Co 
MnO 
.43 
1.00 
28.08 
.42 
2.18 
.54 
CaO 
4.93 
MgO 
25.21 
P 9 R . 
s 
Less 0=S 
101. 24 
.65 
100. 00 
101.09 
1.09 
100. 00 
100.59 

100. 00 
