92 
The American Geologist. 
August, 189M 
ochres. A close examination revealed a spongy mass of iron 
sesqni-oxide, through which was distributed a perfect network 
of white kaolinized masses of the original feldspar. 'J'o the 
unaided eye the mass seemed thoroughly decomposed with- 
out any trace of the original silicate minerals preserved, but 
after removing the iron oxide by continued digestions with 
very dilute hydrochloric acid, and the residue subsequently 
examined under the microscope, considerable traces of both 
undecomposed feldspar and augite were distinctly recogniz- 
able, with surprisingly large quantities of magnetite. Ap- 
parently, the magnetite was in as fresh a condition and in as 
large quantities as in the fresh and unaltered rock. 
DIAMETER IN MM. 
CONVENTIONAL NAMES. 
PER CT.* 
(I) 
2 — .1 
Fine gravel. 
0.00 
(2) 
I — -5 
Coarse sand. 
3.21 
(3) 
■5 — -25 
Medium sand. 
13.10 
(4) 
.25 — .1 
Fine sand. 
15-39 
(S) 
.1 — .05 
Very fine sand. 
23-49 
(6) 
.05 — .01 
Sih. 
23.98 
(7) 
.01 — .005 
Fine silt. 
4.16 
(«) 
.005 • — .0001 
Clay. 
14.20 
Total matter 97-53 
Nos. 2, 3 and 4 show clearly to the unaided eye the com- 
pound character of the mass, and when examined under the 
microscope, although the iron oxide masks to a large extent 
the reaction, distinct particles of the undecomposed silicate 
minerals with an abvmdance of magnetite are to be seen. In 
No. 5 the decayed products become more differentiated into 
kaolin and ferrite (iron oxide), with the usual amount of 
magnetite and some of the undecomposed silicate minerals still 
discernible. Nos. 6 and 7 represent highly colored ferrugin- 
ous masses in which a slight sprinkling of the feldspar, augite 
and magnetite, can still be recognized, to a very much less 
degree, however, in No. 7 than in No. 6. No. 8 is a deep buff 
colored mass of fine clay showing no trace of the original 
minerals whatsoever. 
Chemical Analyses and their Discussion. 
Below are given three tables of analyses indicating the 
*These residues were dried over the steam-bath and weighed without 
ignition. 
