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Napa County

  • Napa County Mines and Mineral Resources (circa 1913-1914) - Excerpts from Report XIV of the State Mineralogist - Mines and Mineral Resources of Portions of California, Chapters of State Mineralogist's Report - Biennial Period 1913-1914, Part II. “The Counties of Colusa, Glenn, Lake, Marin, Napa, Solano, Sonoma, Yolo,” by Walter W. Bradley, Field Assistant (field work in September, 1913), San Francisco, California, July, 1915, California State Mining Bureau, San Francisco, California, 1916, pp. 173-370.

    "Napa County, with a land area of 783 square miles, is about 50 miles north and south, by 26 miles in width. It runs nearly to a point at both extremities, its southern end touching San Francisco Bay. It is bounded on the east by Yolo and Solano counties and on the west by Lake and Sonoma counties. The main drainage system of the county is that of the Napa Valley; in addition to which, Putah Creek flows across the northeast corner, southeasterly to the Sacramento River. Mt. St. Helena is in the northwest corner, at the junction with Lake and Sonoma counties. The principal mineral resources include quicksilver, cement, mineral water, stone industry, and magnesite; with infusorial earth, limestone, copper, iron, chromite, gold, silver, and mineral paint also occurring, but of minor importance (at least in their present lack of development).

    "The available published records show for Napa County, to the end of 1913, a total value of quicksilver produced of practically $15,000,000, and of mineral water nearly $2,000,000. That these values are below the actual output is known, as there are no segregated figures for mineral water previous to 1894; and also as the product of some of the quicksilver mines was included in the earlier reports of the state's production, under 'various mines.' In fact, the Knoxville mines alone are said to have produced $17,000,000 in quicksilver, while Oat Hill is credited with another $5,000,000, to say nothing of the Aetna and others. There being but the one cement plant in the county, the value of the cement output is included under 'unapportioned,' it being the policy of the Bureau not to make private business public. Magnesite production in Napa County began at the Chiles Valley mines in 1891; but the figures for 1892 and 1893 were not segregated, being combined with those of Alameda County. The value of the materials included under 'stone industry' is showing a healthy, steady advance. Mineral water shows considerable fluctuation, but continues an important factor."

    Stone Industry (in Napa County).

    "Under this heading is included building stone, crushed rock, macadam, paving blocks, rubble, sand and gravel, and sandstone. In the hills along the western side of the Napa Valley basalt occurs, which have been quarried for paving blocks near St. Helena and Napa. At the surface, it appears mostly in the form of boulders which are the results of disintegration along cracks and flow lines. The interior of the boulders is for the most part hard, bluish and compact. There are occasional vesicles. Along the eastern side of the valley trachytic tuffs are abundant. There is considerable variation in texture and hardness, but much of it is suitable for rough work such as bridges, walls, and rubble construction. Wooden and iron bridges throughout Napa County have gradually been replaced by stone. The same liberal policy is also maintained by the county in road construction and repairs; that it is a pleasure to ride or drive over its well-kept roads with their picturesque stone bridges (see photos Nos. 35 and 43). The rock is taken from the quarry nearest to the point where it is to be utilized. Napa County is more fortunately situated than many other counties of the State in thus having close at hand an abundant supply of stone suitable for such purposes. Even where stone work is more expensive than in this county, it would still be economical in the long run as it make a more permanent structure as well as picturesque, when compared to wood or even steel.

    "Sandstone is found in the ridges surrounding Berryessa, Pope and Wooden valleys, which are east of the main Napa Valley."

    Photo No. 35. "Little Trancas" bridge, near Napa, Napa County. Stone from Wing Quarry, 1908. "Little Trancas" bridge
    Photo No. 43. "Big Trancas" bridge, near Napa, Napa County. Stone from Wing Quarry, 1913. "Big Trancas" bridge
  • Napa County Mineral Industry (circa 1919) - Excerpt from California Mineral Production for 1919, Bulletin No. 88, by Walter W. Bradley, California State Mining Bureau, 1920, pp. 155-156.

    Area: 783 square miles.
    Population: 20,678 (1920 census)
    Location: Directly north of San Francisco Bay - one of the 'bay counties.'

    "Napa, because of its production of structural and industrial materials and quicksilver, stands thirty-fifty on the list of mineral-producing counties in California. Its mineral resources include chromite, copper, cement, gypsum, magnesite, mineral water, quicksilver, sandstone, and miscellaneous stone.

    "In 1919, the value of the output decreased to $275,303 from the 1918 figure of $1,676,367, due mainly to cement and magnesite.

    (Headings for the information below are: Substance, Amount, and Value.)

    Magnesite, 10,112 tons, $86,752
    Mineral water, 76,860 gals., $60,395
    Quicksilver, 644 flasks, $58,140
    Stone, miscellaneous, ---, $70,016
    (Total value) $275,303

    Napa County, 1916 Map, from California Mineral Production for 1919 (with County Maps), Bulletin No. 88, by Walter W. Bradley, California State Mining Bureau, San Francisco: California State Printing Office, 1920, pp. 187. Napa County , 1916 Map
  • Napa County Mines and Mineral Resources (circa 1948), “Mines and Mineral Resources, Napa County,” by Fenelon F. Davis, Assistant Mining Engineer, California State Division of Mines, Manuscript submitted for publication September 1947, in California Journal of Mines and Geology, Vol. 44, No. 2, April 1948, State of California, Department of Natural Resources, Division of Mines, pp. 159-188. (Used with permission, California Department of Conservation, California Geological Survey.)


    “Napa County, bordering San Pablo Bay, is one of the original 27 counties formed in 1850. The county seat, Napa (city), is about 45 miles north of San Francisco on Highway 29. The county is characterized by mountain ranges and intermountane valleys which trend northwestward, and lie in the southern part of the northern Coast Ranges of California. The surface rocks exposed here include a northern area of Jurassic Franciscan sediments and associated basic intrusives, strips of Shasta (Cretaceous) sediments along the eastern and western borders, patches of Eocene and Miocene sediments in the south, and extensive Pliocene volcanics east of Napa Valley.

    “Napa County ranked thirtieth among the 58 counties of the state in value of mineral production in 1945. The value of mineral production in 1946 was $1,019,786 and was derived from mineral water, pumice, quicksilver, sandstone, and miscellaneous stone. The recorded value of mineral production for 1862 to 1947 was $45,134,431.

    Chrysotile asbestos occurring in a serpentine area 18 miles northeast of Napa was mined from 1941 to 1945. It was milled in a modern electrically operated plant at the mine and the finished product was used as insulating materials, plaster, and stucco, for war housing and war-plant buildings.

    Chromite is found in northeastern Napa County associated with serpentine masses. A total of 2132 tons of chromite was shipped between 1916 and 1941. Shipments during the war years 1941-45, when high prices for chrome ore prevailed, constituted only 19 percent of all the chromite reaching the market from Napa County.

    Clays from Napa Valley have been used in brick and cement.

    Magnesite was produced form 1916 to 1924. Sea water magnesia has largely replaced the product of the magnesite mines except in the case of extremely large high-grade deposits.

    Manganese deposits are numerous in northern Napa County interbedded with sediments of the Franciscan formation. About 300 tons of oxide ore was produced in 1918.

    Mineral water has made important contributions to the annual value of mineral production. Although the present rate of production is comparatively low it is capable of expansion in the near future. The numerous mineral springs have made Napa County famous as a center of rest and recreation resorts.

    Obsidian is potentially valuable as a source of synthetic pumice for use in lightweight building materials. It occurs as a phase of the Pliocene volcanics in the vicinity of Glass Mountain, from which locality it has been traced about 2 miles to the north as a flow.

    Petroleum has been produced from the Jurassic sediments of the Knoxville formation in Berryessa Valley at the rate of half a barrel per day.

    Pumice occurs on the east side of the Napa Valley as pumiceous tuff and breccia in the thick group of Pliocene volcanics. It was capped by a trachyte flow, part of which has been removed by subsequent uplift and erosion. Present mining operations are 3 to 7 miles east of Napa along Highway 37 in areas where there is no overburden. The pumiceous tuff is removed by scrapers, crushed, washed, dried, and used as an aggregate in building bricks and blocks.

    Quicksilver has contributed more to the value of Napa County production than any other mineral. Production figures are recorded for every year since 1862. The first boom period occurred from 1874 to 1878 and another occurred from 1893 to 1899. Since the latter period, production has dropped to a comparatively small figure which has been influenced greatly by fluctuations in price. Mining operations have been chiefly underground although the only present mine (1947) is an open-pit operation. Some creek gravels have been worked on a small scale. The unstable price structure has discouraged the development of reserves in advance of ore extraction.

    Silver sulphides associated with gold in quartz veins were discovered on the slopes of Mount Saint Helena about 1870. Two productive mines were developed, which operated intermittently. More than $1,370,216 in combined silver and gold production between 1874 and 1940 has been reported from Napa County. No production has been reported since 1940.

    Building stone, chiefly sandstone and tuff, has appeared in the production figures from Napa County since 1913. Much of the tuff was used in local construction within the county. Production of miscellaneous stone, which includes crushed rock and sand and gravel, was first reported in 1902. This mineral product reached a substantial figure by 1908 and has been a consistent contributor to the value of mineral production since that date. One of the largest rock plants of the San Francisco Bay area is located at Napa. There are also consistent smaller producers.


    “The American settlers in Napa County were preceded by the Indians and the Spanish explorers. The Pomo Indians established a fishing village or ‘nappo’ on the shore of the bay, and to this word the name ‘Napa’ traces its origin. The first white settler, George C. Yount, received a land grant (Rancho Caymus) in 1835, which was followed by additional grants to other settlers during the forties. Napa was one of the original 27 counties formed in February 1850.

    (* Footnote 1, pp. 160: Hoover, M. B., Historic Spots in California, counties of the Coast Range, pp. 279-299, 1937.

    Gunn, H. L., and Hunt, marguerite, History of Solano and Napa Counties, vol. 1, pp. 270-271, 1926.)

    Geography* (of Napa County)

    “Napa is one of the counties bordering San Pablo Bay. The county seat, Napa (city), is about 45 miles north of San Francisco on State Highway 29. The county is approximately 20 miles wide, 40 miles long, and includes an area of 790 square miles. It is bounded on the west by Sonoma County, on the north by Lake County, on the east by Yolo and Solano Counties, and on the south by San Pablo Bay.

    (* Footnote 2, pp. 160: California Blue Book, p. 601, 1946.)

    “The population (28,503) in 1940 was classed at 25 percent urban and 75 percent rural. These percentages shifted in favor of the urban centers during the war years with the influx of workers to the West Coast industries. The estimated county population in 1946 was 42,700. The urban population figures in 1946 were as follows: Napa 13,500, Saint Helena 2100, and Calistoga 1250, representing about 40 percent of the total.

    “The climate at Napa (city) is typical of a large part of the county. Here the mean temperature ranges from 47° Fahrenheit in January to 67° Fahrenheit in July. The average annual rainfall of 22.7 inches at Napa is exceeded both on the mountain slopes and at the head of the Napa Valley. It has reached a maximum of 60 inches on Mount Saint Helena. These favorable temperatures, coupled with the presence of numerous hot springs, have made Napa County a California vacation land for decades.

    “The Southern Pacific railroad serves the Napa Valley towns as far north as Calistoga and a number of bus lines connect with the smaller communities. There are 114 miles of paved state highways including Highway 29 running north from Oakland on the eastern shore of San Francisco Bay. State Highway 37 leads from Napa to the quicksilver district at the north end of the county and Highway 28 is a connecting link with the Sacramento Valley to the east. An additional 450 miles of county roads make all points in the county accessible by automobile. The Napa River is navigable for vessels of 12 ½-foot draft. A 622-acre airport at Napa, a class 4 port, has two 5,000-foot runways and can handle the largest commercial planes now operating.

    Topography (of Napa County):

    “The area covered by Napa County is in the southern part of the northern Coast Ranges of California. It is characterized by mountain ranges and intermountane valleys which northwestward and slope southeastward. Tributary canyons are normal to the main trend. In the southwestern half of the county is Napa Valley, about 3 miles wide and 40 miles long, through which the Napa River flows to the sloughs of San Pablo Bay at the southern boundary of the county. Elevations here range from sea level at the valley mouth to 600 feet at the valley head, and then rise rapidly in the next 3 ½ miles to 4200 feet in the Mayacmas Mountains at the northwest corner of the county.

    “The northeastern half of the county is separated form Napa Valley by the Howell Range, a southeastern extension of the Mayacmas Mountains of Lake and Sonoma Counties. The area beyond the Howell Range is the locus of a number of smaller valleys, the most important of which are Chiles, Pope, and Berryessa. Of these, Berryessa Valley, 4 miles west of the county’s east boundary, is the largest, averaging over 2 miles in width and 10 miles in length. The area is drained chiefly by Pope, Putah, and Eticurra Creeks, which enter Berryessa Valley from the west, northwest, and north, respectively, and merge into Putah Creek on the west side of the valley. From this point Putah Creek flows southeastward through Berryessa Valley for 7 miles, then winds through the mountains an additional 7 miles to the county line, and continues eastward, emptying into the Sacramento River sloughs in Yolo County.

    “Topographic maps on a scale of 1 to 62,500 or about 1 inch to 1 mile are available for the entire county. The following quadrangles of the United States Geological Survey cover parts of the county: Calistoga, Capay, Carquinez, Mare Island, Morgan Valley, Saint Helena, and Santa Rosa. The remainder of the county is covered by quadrangles of the Corps of Engineers, United States Army, namely, Mount Vaca, and Sonoma. In addition, the United States Geological Survey has published the Napa quadrangle on the scale 1 to 125,000, or about half an inch to the mile. This Napa quadrangle includes the area covered by the Carquinez, Mare Island, Mount Vaca, and Sonoma quadrangles, the city of Napa being in the center of the map.

    Geology (of Napa County)

    “The general surface geology of Napa County is shown on the Geologic Map of California,* scale 1 to 500,000, or approximately 1 inch to 8 miles. The map shows a belt of Cretaceous sediments of the Shasta group outcropping along the entire eastern border of the county and extending westward to an average width of about 4 miles. This belt is flanked on the west by a parallel strip of Knoxville sediments and about 1 ½ miles in width extending from the north boundary to the south end of Berryessa Valley. The remainder of the county north of T. 7 N. is covered by Franciscan sediments and their associated basic intrusives. The east flank of Napa Valley is composed of a thick group of Pliocene volcanics. On the west flank of the valley the Shasta is again exposed and is partly overlain by the Pliocene volcanics which extend westward under the valley alluvium.

    (* Footnote 3, pp. 162: Jenkins, Olaf P., Geologic map of California, scale 1:500:000, California Div. Mines, 1938.)

    “Two geological cross sections running northeastward through Napa County were made by Osmont.* The first section passes through Mount Saint Helena, Oak Hill, and Knoxville. The second section passes through the city of Napa. These sections are accompanied by a detailed discussion of the geological formations encountered en route.

    (* Footnote 4, pp. 162: Osmont, Vance C., Geological section of the Coast Ranges north of the bay of San Francisco: Univ. California Dept. Geol. Sci. Bull., vol. 4, pp. 39-87, 1904.)

    “References to additional reports on Napa County chromite, clay, magnesite, manganese, petroleum, and quicksilver will be found in the sections devoted to individual minerals.

    Industries (in Napa County circa 1948)

    “Farming is the chief industry of Napa County. The value of agricultural crops produced in 1945 was $12,938,750, being derived from prunes, grapes, poultry, miscellaneous orchard and field crops, dairy products, and animal production. Industrial Napa lies almost at the exact center of Pacific Coast population. Excellent transportation, ample gas and electric facilities, a good municipal water supply, and abundant petroleum products from nearby refineries, have helped factories locate here. The present industrial output includes wearing apparel, gloves, paper, leather, wine, and steel products.

    Mineral Resources (in Napa County)

    “Napa County ranked thirtieth among the counties of the state in value of mineral production in 1945. The minerals produced in 1946 were mineral water, pumice, quicksilver, sandstone, and miscellaneous stone, having a total value of $1,019,786. Other mineral products have been asbestos, building stone, cement, chromite, clay, copper, gold, lead, limestone, magnesite, manganese, onyx, paving blocks, petroleum, sandstone, and silver. The important mineral products are described in alphabetical order below. Figures showing annual production and value are presented in table 1.”

    (Note: Only the “Stone Industry” section will be presented here. The following sections will NOT be presented here: Asbestos, Chromite, Clay, Magnesite, Manganese, Mineral Water, Obsidian, Perlite, Petroleum, Pumice, Quicksilver, Silver, and Rock and Sand companies.)

    Stone Industry (in Napa County), pp. 184-188.

    “There were formerly a number of small quarries in Napa County which produced sandstone or tuff blocks for bridges and the cut-stone industry, and the general acceptance and use of lower-priced concrete construction has nearly eliminated the production of building stone, not only in the county but throughout the state.

    “‘Miscellaneous stone’ is a term used to include crushed rock, sand and gravel, paving blocks, and grinding-mill pebbles. This usage has developed from the fact that an individual operator often produces sand and gravel from a stream bed, using the large boulders as the source of his crushed material. Crushed rock is often further subdivided on a usage basis into macadam, ballast, rubble, riprap, and concrete aggregate, although it is not always possible to determine the final disposition of the product.

    (Note: Please see the following entry titles listed below in the “Napa Quarries” section of this web site for information on the following companies:

    Basalt Rock Company, Incorporated (located 2 ½ miles south of Napa on Highway 29, and 1 mile east of the Napa River)

    Juarez Quarry (located approximately 2 miles east of Napa station off Terrace drive on the south side of Tulucay Creek.)

    Lenz and Son Basalt Quarry and Plant (located about 2 ¼ miles northwest of Saint Helena on Highway 29 and half a mile west of the Southern Pacific railroad.)

  • Napa County Limestone (through) 1949 (From Geology and Mineral Deposits of an Area North of San Francisco Bay, California: Vacaville, Antioch, Mount Vaca, Carquinez, Mare Island, Sonoma, Santa Rosa, Petaluma, and Point Reyes Quadrangles, Bulletin 149, by Charles E. Weaver, California State Division of Mines, September 1949. Used with permission, California Department of Conservation, California Geological Survey.)

    "Limestone, though not widely distributed in the area investigated, once helped to support two cement plants. The Standard Portland Cement Company used an argillaceous limestone interstratified with Cretaceous beds near Napa Junction; travertine supplied the Pacific Portland Cement Company's plant at Cement. The pure crystalline limestone deposit which occurs in granodiorite west of Tomales Bay has not been exploited.."

    "The limestone deposit southeast of Napa Junction from 1903 to 1908 furnished material to a plant owned by the Standard Portland Cement Company. The limestone is interbedded with Knoxville shales and ranges from argillaceous varieties to pure limestone. The deposit is described* as containing regular beds of limestone from 1 foot to 4 feet thick, striking N. 70 E. and dipping 65 NW., which are overlain by a yellow calcareous clay. About 100 feet of limestone and 50 feet of the clay were exposed in the pit from which both materials were obtained. It is stated that the clay became more calcareous toward the east and merged into limestone. This company also failed after an attempt was made to supplement the local limestone with material brought from near Santa Cruz.."

    (* Page 88, footnote 70: Logan, C. A., Limestone in California: California Jour. Mines and Geology, vol. 43, p. 332, 1947.)

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