MAGMATIC DIFFERENTIATION OF IGNEOUS ROCKS 533 
No. 49: Websterite, composed only of bronzite and diallage. Hebbville 
near Baltimore. G. H. Williams, Amer. Geologist, Vol. VI; F. W. Clarke, 
U.S. Geol. Sur. Bull. 228 (1904), p. 51.—No. 50: Pikrite. Schwarzenstein, 
Fichtelgebirge. In the rock 0.09 percent CO,. Giimbel, Geogr. Beschreibung 
Bayeryns, 1879. (Rosenbusch, Gesteinslehre, p. 352.)—No. 51: Hypersthene 
diabase. Twins by Rapidan, Virginia. Campbell and Brown, Bull. Geol. Soc. 
Am., II.—No. 52: Diallage-hornblende-gabbro. Veltein, in the Alps. Kiich- 
ler, Chemie der Erde, I, 1914. The analysis of the rock from Hecker, Neues 
Jahrb. f. Min., Geol. u. Pal., Beil., Bd. XVII (1903).—No. 53: Hypersthene- 
biotite-dacite. Upway, Victoria. Skeats, Quart. Jour. Geol. Soc. London | 
1910. In the rock 0.16 per cent S. In the biotite H.O+, 3.20 and H,0+, 
0.43 per cent.—No. 54: Kimberlite, strongly decomposed. From Elliot 
County, Kentucky. In the rock 8.92 per cent H.O, 6.66 COn, 0.28 SO;, 
0.05 NiO. Diller, U.S. Geol. Soc. Bull. 38, and Amer. Jour. Sci., 3d Series, 
Vol. XXXII; Clarke, U.S. Geol. Soc. Bull. 228, p. 66. 
OLIVINE AND ORTHORHOMBIC PYROXENE 
We shall commence with some analyses of olivine and bronzite 
from olivine nodules in basalts. We shall base the calculations for 
the bronzite, often somewhat decomposed, on the entire quantity 
of iron found analytically. In reality a little, but only very little, 
iron in the bronzite will appear as Fe.O,. 
The stoechiometric relation between MgO and FeO in olivine 
and bronzite for olivine nodules: 
Sidi 55a ~_—{ Olivine 1 MgO:o0.11 FeO 
(Kappenstein, etc.).... 550 | Bronzite t MgO:o0.14 FeO 
: 56a Olivine t MgO:o0.11 FeO 
565 Bronzite t MgO:o0.10 FeO 
57a ee t MgO:0.09 FeO 
Dreizer Weiher, Eifel.... ) 578 Bronzite 1 MgO:o. 11 FeO 
: 58a Olivine 1 MgO:o0.11 FeO 
586 Bronzite t MgO:0.10 FeO 
St 1, Marb Fu toes 598 Olivine t MgO:o.10 FeO 
ace aes { 59) Bronzite t MgO:o.11 FeO 
Kaiserstuhl, Baden ..... Gog Olivine 1 MgO:0.09 FeO 
5 606 Bronzite t MgO:o.10 FeO 
Reihenweiler, Alsace .... one Olivine 1 Mg0:0.14 FeO 
; 616 Bronzite 1 MgO:0.14 FeO 
Nos. 55a, 6, and c: Kukurzenkezel near Kappenstein: Schadler, Tscherm. 
Miti., Vol. XXXII (1914).—No. 56a and 6: Schiller, Becke, Tscherm. Mitt., 
Vol. XXIV.—Nos. 57a and b: Th. Kierulf, Bischof’s chem. Geol., and Pogg. 
