CLARKE.] 
IGNEOUS AND CRYSTALLINE ROCKS. 
DELAWARE. 
49 
Feldspars from gabbros. Separated byDiller, described by Chester 
in Bull. 59. Analyses by R. B. Riggs, record Nos. 459, 400, 461. 
A. Sp. gr., 2.592 to 2.877, from a typical gabbro, Brandy wine Creek, 
Wilmington. 
B. Sp. gr., 2.592 to 2.780, from a typical hypersthene-gabbro, Fifth 
and Van Buren streets, Wilmington. 
C. Sp. gr., 2.592 to 2.749, from ''Iron Hill hyperite changing to 
diorite," near Whitaker's ore pit. 
Si0 2 . 
A1,A 
Fe 2 O a 
MgO 
CaO. 
Na 2 
K 2 0. 
MnO 
Ign . 
A. 
B. 
70. 37 
51. 44 
L8.36 
30. 05 
.58 
.96 
.04 
trace 
5. 08 
13. 19 
4.32 
4.07 
.63 
.21 
trace 
.45 
.35 
99. 83 
100. 27 
c. 
44.09 
35.41 
.51 
none 
18.47 
.99 
.19 
trace 
.35 
100. 01 
Samples dried at 105°. FeO not determined separately 
Bull. 228—04 i 
