Page 178 - 1915, Springs of CA.

162 SPEINGS OF CALIFORNIA.

The following analysis of the material by Roger C. Wells indi-
cates that at least a part of the deposit has come into a stable con-
dition with regard to its content of moisture and may be the mineral
hydrogiobertite (MgCO3.Mg(OH)2 + 2H2O), though other parts of the
specimen examined had a somewhat different composition.1 A speci-
men that was examined microscopically by W. T. Schaller appeared
to consist of two intergrown minerals.
Analysis of material from spring deposit at Phillips Soda Springs, Napa County, CaL
[Analyst, R. C. Wells, 1910.]
Insoluble in hydrochloric acid 2 ................................ 25. 37
Soluble in hydrochloric acid:
Iron and alumina (Fe2O3+Al2O3).......................... 1. 88
Calcium oxide (CaO)....................................... 2. 57
Magnesium oxide (MgO).................................... 31. 81
Carbon dioxide (CO2)....................................... 18.07
Sulphate (SO4)............................................. None.
Water (H2O)............................................... 19.94
99.64
Along the front of this deposit, where it has been cut into by the
surface water, there is a bluff that exposes- a structure resembling
a stockwork, in which veins and masses of the cementing material
inclose fragments of dark shale.
Phillips and Napa Rock springs issue at the lower border of an
area of serpentine that apparently overlies the shale forming the
lower portion of the hills. The association of serpentine with mag-
nesium waters is here again clearly shown, but the large spring
deposit of a magnesium carbonate is believed to be an uncommon
formation. The only other notable one of the kind that was observed
in the State was near the Hot Springs at Elgin mine, in Colusa
County, but the deposit at Phillips Springs differs from the hard
compact material found there.
GAILLATJMES SODA SPRINGS (NAPA 6).
In a ravine about 6 miles northwestward across the hills from
Phillips springs on the Gaillaume ranch are two or three small car-
bonated and sulphureted springs that have been occasionally visited
by campers, but in 1910 they had not attained importance. The
rocks at these springs are part of the sedimentary series that covers
most of this region.

TOLENAS SPRINGS (SOLANO 1).
In the Coast Ranges there are two notable deposits of calcium
carbonate in the form of onyx marble or Mexican onyx which seem
to be essentially spring deposits and near which carbonated water
1 Wells, R. C., A new occurrence of hydrogiobertite: Am. Jour. Sci., 4th ser., vol. 30, pp. 189-190,1910.
2 The insoluble portion had the appearance of soft grains resembling shale.