L86 
ANALYSES OF ROOKS, U. S. GEOLOGICAL SURVEY. [no. 228. 
F. Tinguaite?, Two Buttes. Laurdalose. Collected by G. K. Gil- 
bert; petrographic data supplied by Whitman Cross. Consists chiefly 
of pale-green augite, hornblende, apatite, magnetite, and occasional 
crystals of alkali feldspar, in an obscure, largely isotropic ground- 
mass. Sp. gr., 2.79, 25°. P. R. C. 1393. 
G. Pyroxene from F. Sp. gr., 3.43, 28°. 
H. Portion of F soluble in ^ nitric acid. 
I. S} T enitic lamprophyre?, Two Buttes. Prowersose. Collected by 
Gilbert; description by Cross. Chief constituents, diopside, alkali 
feldspar, considerable biotite, magnetite, and olivine. The ferromag- 
nesian minerals predominate. Sp. gr., 2.88, 29°. P. R. C. 1394. 
J. Pyroxene from I. Sp. gr., 3.15, 25°. 
K. Portion of 1 soluble in ^ nitric acid. 
Analyses F to K by W. F. Hillcbrand, record No. 1604. 
Si0 2 .. 
AlA- 
FeA 
FeO.. 
MgO. 
CaO.. 
Na 2 0. 
K 2 0.. 
H 2 above 110 c 
Ti0 2 
PA 
Zr0 2 
CrA 
VA-- 
NiO 
MnO ... 
SrO 
BaO 
Li 2 
S0 3 
s 
CI... 
F 
47.61 
14. 26 
4.90 
4.07 
2.62 
s. 71 
6. 70 
4.08 
.26 
L.89 
1.38 
1.38 
.18 
trace? 
trace 
.30 
.36 
.41 
trace 
1.17 
.03 
.37 
trace 
100. 68 
G. 
47.54 
4.14 
5.64 
6.42 
10.05 
21. 57 
1.38 
.12 
none 
undet. 
3. 00 
none 
trace? 
trace 
.36 
none 
none 
trace 
100.21 
][. 
13. 27 
9.40 
trace 
trace 
1.70 
5.41 
.66 
nndet. 
undet. 
1.34 
trace 
.11 
none 
(?) 
. 77 
.03 
.37 
trace 
33. 06 
50. 41 
12.27 
5.71 
3. 06 
8. 69 
7.08 
.97 
7.53 
.46 
1.80 
1.47 
.46 
none 
trace 
.03 
.04 
.15 
.06 
.23 
trace 
none 
none 
trace 
trace? 
100.42 
51. 27 
3.05 
3. 08 
4. 34 
14.21 
22.58 
.67 
.06 
none 
undet. 
.70 
none 
none 
.03 
.28 
none 
none 
100. 2: 
1.58 
1.00 
none 
.87 
1.22 
.68 
undet. 
undet. 
none 
undet. 
46 
trace 
(?) 
none 
trace 
5.81 
