ILLUSTRATIONS.

Page.

PLATE I. Map of California, showing distribution of magnesite deposits.
II. Specimens of magnesite, showing conchoidal fracture
III. Weathered surfaces of magnesite.....

IV. A, Small irregular vein of magnesite in serpentine; B, Magnesite
weathered under several inches of clay

V. A, Outcrop of magnesite on Hixon ranch, Mendocino County; B,
Entrance to lower tunnel on Sonoma Magnesite Company's claim,
near Cazadero; C, Outcrop of magnesite vein on Walters claim,
Pope Valley.....

VI. Cracks in magnesite apparently due to shrinkage: A, Compact
magnesite from the Hixon ranch, Mendocino County; B, Less
compact magnesite coated with a thin layer of quartz, also
cracked, from locality 4 miles northeast of Porterville....

VII. Structure of magnesite on Bay Cities Water Company's land on
Coyote Creek: A, Specimen from the upper deposit, showing a
natural surface; B, Specimen from the lower deposit, showing
a smoothly ground surface....

VIII. A, Stockwork of magnesite veins 3 miles south of Winchester;
B, Sheeted serpentine containing many thin veins of magnesite
near Deer Creek, Tulare County....

IX. A, Amphibolite dike cutting through flat vein of magnesite; B,
Crushed magnesite vein near Porterville,.....

X. Northern hill at the Willamette Pulp and Paper Company's mag-
nesite mine near Porterville: A, Nearly vertical vein; B, Lower
"blanket" vein..................

XI. A, Outcrop of stockwork of veins at north end of Willamette Pulp and
Paper Company's deposits near Porterville; B, Furnace for calcin-
ing magnesite at Willamette Pulp and Paper Company's magnesite
mine near Porterville...

XII. A, Magnesite vein on south side of Kings River, 9 miles east of
Sanger, Cal.; B, Magnesite vein on Snow Cap claim, north side of
Kings River, 9 miles east of Sanger...

FIG. 1. Diagram of Western Carbonic Acid Company's plant at Sedan, Cal....
2. Plan of magnesite veins and workings 4 miles northeast of Porter-
ville, Cal....

3. Diagram showing mode of working a highly inclined magnesite vein
at Willamette Pulp and Paper Company's mine near Porterville, Cal.
4. Elevation and plan of Willamette Pulp and Paper Company's furnace,
4 miles northeast of Porterville, Cal

5

THE MAGNESITE DEPOSITS OF CALIFORNIA.

By FRANK L. HESS.

GENERAL REMARKS.

INTRODUCTION.

Magnesite, or magnesium carbonate, ordinarily occurs in veins or in masses replacing other rocks rich in magnesia, though it seems probable that a few isolated and impure deposits in Quebec are of sedimentary origin. (See p. 53.) Although it can hardly be classed as a common mineral, it exists in comparatively large deposits at many places in various parts of the world. The principal foreign deposits now worked are in Austria, Greece, India, Italy, Norway, Russia, and South Africa. Other deposits which are either not worked or from which the output is small occur in Africa, Australia, British Columbia, Lapland, Mexico, Quebec, and Venezuela.

In the United States the only important deposits known are in California. Small veins of mineralogic interest only have been noted in Pennsylvania, Maryland, and Massachusetts, and veins of unknown extent are reported to exist in Nevada and Arizona.

a

с

The Maryland and Pennsylvania deposits were at one time worked in a small way, the product being used for making Epsom salts (magnesium sulphate) and other chemicals, but magnesite from Austria, Greece, and South Africa can now be imported so cheaply that it no longer pays to operate them.

In California the deposits are scattered along the Coast Range from Mendocino County, and possibly farther north, to a point south of Los Angeles, and along the western slope of the Sierra Nevada from Placer County to Kern County. (See Pl. I.) Deposits are worked in Sonoma County near Cloverdale, in Santa Clara County near Livermore, and in Tulare County near Porterville. Mines were formerly operated in Chiles and Pope valleys, Napa County, and

a Frazier, P., jr., Lancaster County: Second Geol. Survey Pennsylvania, Vol. CCC, 1880, pp. 89, 97, 176-179, 196.

› Bascom, F., The geology of the crystalline rocks of Cecil County: Cecil County report, Maryland Geol. Survey, 1902, pp. 96-97.

© Dana, J, D., A system of inineralogy, 6th ed., 1892, p. 275.