412 W. H. MELVILLE CHEMISTRY OF THE MOUNT DIABLO ROCKS. 



Series VI — Analyses of Tertiary and Cretaceous Sandstones. 



(11) (187) (59) (83) 

 abed 



H,0 at 100° C 1.06 1.45 1.43 0.57 



H2O above 100° C 2.60 3.34 2.25 3.45 



CO, none 5.10 7.76 *11.30 



SiO, 73.71 56.84 44.54 36.93 



P.,05 none 0.10 0.29 0.16 



Al.Og 10.40 11.37 12.63 7.22 



Fe203 3.89 1.46 2.50 1.59 



FeO 1.88 4.95 3.08 2.95 



MnO 0.17 0.22 0.44 0.57 



CaO 0.96 7.62 14.65 29.34 



MgO 1.62 3.10 5.55 2.34 



Na.,0 3.48 3.26 3.35 2.94 



K26 0.99 0.86 1.37 0.64 



iOO.77 99.67 99.84 100.00 



Series VII. — From the diabase area in Mitchell caiion, north of the 

 serpentine dike, two specimens were selected. Specimen a was fresh, but 

 specimen h was somcAvhat altered and partly uralitic. The analyses show 

 but slight differences in composition. In this diabase serpentine is absent, 

 and it is not found to yield this hydrous magnesian silicate. It would be 

 necessary to substitute a magnesian silicate for the plagioclase, which has 

 been shown before in the case of shales a difficult and an imperfect opera- 

 tion. Field observations show no relations between the diabase and the 

 serpentine of Mount Diablo as they have shown between the pyroxenite and 



serpentine. 



Series VII — Analyses of Diabase from Mitchell Canon. 



(43) (44) 



a b 



Loss at 105° C 0.59 0.34 



Loss above 105° C 2.90 2.67 



SiO.^ 52.06 51.58 



P2O5 0.13 0.24 



Ti02 0.47 1.05 



Al.,03 14.34 14.99 



Fe203 2.11 2.04 



FeO 7.74 8.36 



MnO trace trace 



CaO 8.05 8.59 



MgO 9.26 6.51 



Na20 1.74 3.08 



K2O 0.73 0.31 



100.12 99.76 



*C0o by difference. Organic matter in very small quantity exists in all four sandstones, but it 

 was not determined. 



