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Los Angeles County

  • Los Angeles County Mines and Mineral Resources (circa 1915-1916) - Excerpts from Report XV of the State Mineralogist, Mines and Mineral Resources of Portions of California, Chapters of State Mineralogist's Report Biennial Period 1915-1916, Part IV. Los Angeles County, Orange County, Riverside County, California State Mining Bureau, 1919, pp. 465-589. Used with permission, California Department of Conservation, California Geological Survey.)

    This report was "prepared by Dr. F. J. H. Merrill from field observations during the summers of 1914 and 1915." Dr. Merrill died in Los Angeles, November 29, 1916.

    Introduction (Los Angeles County)

    "While there is no production of metals here, there is a great wealth of nonmetallic minerals, and their production, in 1914, amounted to $4,665,504. Further, the rapid growth of the city of Los Angeles, and its great consumption of industrial materials, especially those used in building, has led to the erection, within the city limits, of a number of manufacturing plants of much commercial importance which convert raw materials into merchantable products...."

    Organization and Boundaries (of Los Angeles County)

    "This county, organized by act of legislature in February, 1850, lies between 33 45' and 34 50' of north latitude and between 117 36' and 118 50' longitude from Greenwich. Its general form is that of a quadrilateral, measuring about 70 miles from north to south and 65 from east to west.

    "It is bounded north by Kern County, east by San Bernardino and south by Orange County and the ocean, which, together with Ventura County, forms its west boundary, the ocean shore-line amounting to about ninety miles. It comprises five thousand six hundred square miles, or about three million five hundred and eighty-four thousand acres, a large proportion of which is mountainous, and, in the northeast, is occupied to the extent of about twenty townships, by the Mojave Desert, a flat sandy country with little water, cut up by ranges of low hills of Tertiary rocks.

    Physiography (of Los Angeles County)

    "The chief topographic features of this county are the mountain ranges, the valleys, and the great Los Angeles plain which stretches from the foothills to the sea...."

    Nonmetallic Minerals (in Los Angeles County)

    "The nonmetals are commercially the most important among the mineral products of this county. In 1914 their aggregate value was upwards of $4,000,000.

    "The presence here, of the metropolis of southern California, has developed a great demand for materials employed in the building trades."

    Building Materials (in Los Angeles County)

    Building Stone (in Los Angeles County)

    "Not many years ago building stone or rock of attractive appearance and durable qualities which could be cut or dressed to a convenient form and size for building operations was a matter of much importance and a substantial asset to any state or country, but with the lapse of time and the development of new methods of construction, brick, terra cotta, and concrete have been so extensively substituted for cut stone, that the latter has become of minor importance and many deposits of material formerly available and in demand now lie unnoticed. In this report, space will be given only to building stones formerly worked or now in use for special purposes.

    "Among the building stones occurring in this county are the following, although they are not all produced commercially: granite, marble, serpentine, sandstone, volcanic tuff and trachyte.

    Granite (in Los Angeles County)

    "No stone of this class has been worked in this county except by crushing plants for concrete...."

    "Much granite is exposed in the San Gabriel Range but the outcrops are high and inaccessible."

    Marble (in Los Angeles County)

    "No stone of this class has lately been worked in Los Angeles County, though there is a record of a Southern California Marble Company with a quarry operated near Neenach by John Rebman of Los Angeles. This record can not now be verified as Mr. Rebman has moved to Arizona.

    "Crystalline limestone, which, in some localities makes a high class marble, is described by W. A. Goodyear* as occurring in Pacoima Cañon near San Fernando. It does not appear, however, that this material has been used for other purposes than making lime.

    (* Page 481 footnote: Bulletin 38, p. 100; also, R. XIII, p. 629.)

    "Prof. R. T. Hill of the U. S. Geological Survey, states that on the southeast slope of the Tehachapi Range, and the northwest border of the Antelope Valley, limestone outcrops extensively with northeast and southwest strike, dipping steeply into the mountains. The strike of these beds should carry them into the northwest corner of Los Angeles County, but no record can be found that they are now worked there.

    "In Bull. No. 38, p. 100, is a record of this limestone belt as worked in Kern County* in 1906. On page 367 of the same bulletin are data suggesting that it was, at that time, worked in Los Angeles County. In R. XIII, 1896, p. 629, is a note of a marble quarry in Antelope Valley, forty miles northeast of Lancaster. This is clearly incorrect, as the limestone above mentioned lies northwest of Lancaster.

    (Page 482 footnote: See, also, Report on Kern County, 1915.)

    Crushed Stone (in Los Angeles County)

    "The extended and ever increasing use of concrete for buildings and pavements makes the supply of crushed stone a matter of great importance. The stone chiefly crushed in this county for concrete is granite, of which boulders and cobblestones, in immense numbers, are distributed widely over the river washes which form where the mountain streams emerge from their rocky cañons, bearing along, in their torrential flow, great quantities of fragments from the cañon walls. So, it has long been a custom to install crushing and screening plants on these river washes to separate the sand from the cobbles and crush the latter, thus providing two of the most important constituents of concrete. Such crushing plants are operated on the Pacoima, Tujunga, Arroyo Seco, and San Gabriel washes by various companies which will be mentioned in detail.* The economy of this procedure is obvious, as the cost of quarrying the rock from its native ledge is wholly eliminated, the expense of handling small boulders and cobbles being trifling."

    (* The section on "Rock Crushing Plants" will not be presented here.)

    Portland Cement (in Los Angeles County)

    "This important building material is not made in Los Angeles County. The great plants at Riverside, Colton and Oro Grande, make it unnecessary to establish a plant in this county. The County Board of Supervisors, however, controls the large plant built by the City of Los Angeles at Monolith, Kern County, to supply the construction of the new city aqueduct, and this plant is in operation at present."

  • Los Angeles 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. 151-152.

    Area: 4,067 square miles.
    Population: 936,438 (1920 census).
    Location: One of the southwestern coast counties.

    "Mineral production in Los Angeles County for the year 1919 amounted in value to $23,606,381 as compared with the 1918 output, worth $16,606,628. This county ranked third in the state as a mineral producer in 1919, passing Fresno, which was fourth in 1918. The advance was due to the large increase in the petroleum output and valuation.

    "Its output of brick and tile was over a million dollars, and that of petroleum amounted to over twenty million dollars. Among the mineral resources may be noted asphalt, barytes, borax, brick, clay, fuller's earth, gems, gold, gypsum, infusorial earth, limestone, marble, mineral paint, mineral water, natural gas, petroleum, salt, glass-sand, sandstone, serpentine, silver, soapstone, and miscellaneous stone. Some potash has been obtained from kelp.

    "Commercial production for 1919 was as follows:"

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

    Brick and tile, ---, $1,185,154
    Clay, 11,329 tons, $33,343
    Mineral water, 125,400 gals., $8,787
    Natural gas, 4,148,476 M. cu. ft., $458,812
    Petroleum, 15,076,633 bbls., $20,805,754
    Stone, miscellaneous, ---, $715,524
    Other minerals,* ---, $399,007
    (Total value) $23,606,381

    (* Includes borax, gems, graphite, magnesium salts, manganese, and salt.)

    Los Angeles 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. 197. Los Angeles County , 1916 Map
  • Los Angeles County Limestone Industry and Deposits (through 1947) - Excerpt from "Limestone in California," by Clarence A. Logan, California Journal of Mines and Geology, Vol. 43, No. 3, July 1947, California Division of Mines, San Francisco, California, pp. 175-357. Used with permission, California Department of Conservation, California Geological Survey.)

    "Most of the limestone and lime products used in the Los Angeles area have been shipped in, coming in part from Arizona and Nevada, and in part from neighboring counties. However, there are some interesting limestone deposits in the younger geologic formations, and several small deposits of limestone and dolomitic limestone have been noted in the pre-Tertiary crystalline rocks of the Little Tununga quadrangle in the western part of the San Gabriel Mountains. There has been some production of limestone in recent years at Bel-Air and Palmdale, and in the late twenties at Torrance."

  • Los Angeles County Mines and Mineral Deposits (circa 1953) - Excerpts from "Mines and Mineral Deposits of Los Angeles County," by Thomas E. Gay, Jr., Assistant Mining Geologist, California State Division of Mines, California Journal of Mines and Geology, Vol. 50, Nos. 3 and 4, July - October 1954, pp. 467-709. (Manuscript submitted for publication October 6, 1953.) (Used with permission, California Department of Conservation, California Geological Survey.)


    "Los Angeles County covers 4,071 square miles in southwestern California, including rugged mountains, fertile valleys, coastal plain, desert area, and Pacific islands. Except for the desert area in the north the county lies within the Peninsular Ranges and Transverse Ranges geomorphic provinces, characterized by northwest- and west-trending mountain ranges respectively.

    "Sedimentary, metamorphic, and igneous rocks are extensively exposed. Sedimentary rocks, ranging from Cretaceous through Tertiary in age, are distributed widely in the southern and western parts of the county. The principal sites of deposition were the Los Angeles and Ventura basins, with geologic histories that differed at times, but each receiving a total thickness of more than 40,000 feet of sediments.

    "Metamorphic rocks include pre-Cambrian (?) Pelona schist; Triassic (?) Santa Monica slate, phyllite, and schist; and the pre-Cretaceous Catalina series and metamorphic rocks of the San Gabriel Mountains. Various intrusive and extrusive types of igneous rocks, Jurassic (?) and later in age, are exposed in the mountain areas.

    "As a result of its tremendous production of oil and gas, the 1951 mineral production of Los Angeles County was the largest in value of any county in the state. The county's mineral production for that year was valued at $282,948,130. Cement, clay, diatomite, gold, granite, iodine, salt, gravel, silver, soapstone, stone, and titanium concentrates accounted for the rest.

    "The county also leads the state in total value of mineral production. Approximately 90 percent of the recorded $4,524,761,130 in mineral wealth extracted in the county through 1951 has been derived from petroleum and natural gas. The remaining 10 percent includes 28 mineral substances: asphalt, barite, borax, clay, copper, dolomite, diatomite, feldspar, gem stones, gold, graphite, gypsum, iodine, lead, limestone, magnesium chloride, manganese, marble, mineral water, miscellaneous stone, potash, salt, silica, silver, sulphur, talc, titanium, and zinc.

    "Nonmetallic minerals, led by sand, gravel, and crushed rock, common clay, and diatomite, account for the bulk of the county's production. Most of the sand, gravel, and crushed rock operations in the Big Tujunga Wash in San Fernando Valley. Common clay from numerous sites near industrial Los Angeles is used to make brick, tile, and sewer pipe. Diatomite is produced from a large deposit on the north side of the Palos Verdes Hills. Brines from certain oil wells in several oil fields are the source of all the crude iodine produced in the United States (circa 1953).

    "Gold, with a total recorded production of more than $2,258,000 through 1950, leads the metallic minerals in value. Most of this output has been obtained from the quartz veins of the Governor mine near Acton. Lead, silver, and zinc were produced from 1919 to 1929 from deposits on Santa Catalina Island. Large reserves of titaniferous magnetite occur in the western San Gabriel Mountains. Several concentrations of titaniferous magnetite sands in stream beds and beach deposits have been mined.

    "The Los Angeles basin is the most productive oil-producing region of its size in the world. Wells in the county have yielded more than 3 billion barrels of oil and 3 ½ million cubic feet of gas through 1952 obtained from 37 separate fields in the Los Angeles and Ventura basin. Oil has accumulated in sandstones of lower Pliocene and upper Miocene age and in fractured pre-Cretaceous metamorphic rocks.

    Introduction* (Los Angeles County)

    (* Page 469 footnote: California Blue Book, 1950; Hastings House, 1941.)

    "Exploration of the Los Angeles region began as early 1542, when Juan Cabrillo discovered Santa Catalina Island and what is now San Pedro Bay. The site of the present City of Los Angeles was not seen by white men until 1769 when the Portola expedition, traveling north to find the Bay of Monterey, encamped near the Indian village of Yang-n in an area now occupied by Elysian Park.

    "The pueblo of Los Angeles, one of the first settlements to be established in California, was founded in 1781 under the authority of Carlos III, King of Spain. Until the Mexican War and the American occupation, Los Angeles grew slowly but consistently in population. In 1850, when Los Angeles County had a population of 8,329 and the city of Los Angeles had a population of 1,610, the city was incorporated and made the county seat.

    "Los Angeles County was organized in 1850 as one of the 27 original counties of California. In 1851 its boundaries were extended to include most southern California between Santa Barbara and San Diego, an area of some 31,000 square miles, reaching eastward to the state line.

    "In 1853 the present eastern boundary was established through the formation of San Bernardino County. In 1866 the present northern boundary was defined with the creation of Kern County, and in 1889 the southern boundary was revised to its present position, with the establishment of Orange County. Los Angeles County now contains 4,071 square miles and measures about 75 miles from north to south and 70 miles from east to west.

    "During the late 1800s Los Angeles grew slowly, but in the twentieth century the city and the surrounding area experienced a phenomenal population and industrial growth. The Los Angeles area is now one of the great port cities of the world, one of the great railroad centers of the country, and the third largest manufacturing city in the United States (circa 1953). Sharing in this growth are the smaller cities and towns in Los Angeles County.

    "The population of Los Angeles County was 4,125,000 in April 1950, an increase of 48 percent over 1940. About 79 percent of the residents of the county live inside incorporated cities and the remainder live in unincorporated towns or rural areas.

    Geography (of Los Angeles County)

    "Los Angeles County is in the southwestern part of California and is bounded by Kern County on the north, San Bernardino and Orange Counties on the east, Ventura County on the west, and the Pacific Ocean on the west and south.

    "Four main physiographic features stand out in Los Angeles County: (1) the coastal plain, known also as the Los Angeles basin, which borders the ocean on the north and east; (2) the structurally similar San Fernando and San Gabriel Valleys, separated from the coastal plain and from each other by low hills; (3) the massive San Gabriel Mountains, north of the San Gabriel Valley and San Fernando Valley; and (4) the Mojave Desert in the northernmost part of the county, its western part known as Antelope valley...."

    Limestone, Dolomite, and Cement (in Los Angeles County)

    "Production of lime and limestone in Los Angeles County dates back to the Spanish period prior to 1800. Lime kilns were built by the Spaniards and early American settlers for burning locally mined limestone to provide lime mortar for construction purposes. With the advent of portland cement, lime mortars were supplanted by cement mortars, and masonry by concrete. Although lime products still are important constituents in various construction materials the largest tonnage of lime used by construction industries is in the form of portland cement."

    "Calcium carbonate (CaCO3), alumina (Al2O3), and silica (SiO2) are the three essential constituents used in the manufacture of portland cement. The most common source of calcium carbonate is high-calcium limestone; some form of clay usually supplies the alumina and silica. Being of low cost per unit weight, cement is generally manufactured as close to centers of population as the availability of raw materials will allow in order to minimize transportation expenses. Although the construction industry in Los Angeles area consumes the bulk of the cement manufactured in southern California, limestone suitable for cement manufacture is not abundant in the county.

    "The portland cement industry in southern California has developed in San Bernardino and Riverside Counties where large deposits of high-calcium limestone exist. The only cement plant in Los Angeles County, that of the Blue Diamond Corporation, receives most of its materials from San Bernardino and Riverside Counties...."

    "Small amounts of limestone, dolomitic limestone, and calcareous material have been mined in Los Angeles County, yielding material for poultry grit, roofing granules, building stone, soil additives, and other minor uses. These operations have generally been small and intermittent. In 1952 production of limestone in Los Angeles County was restricted to two operations. The Amercal deposits yielded roofing granules and soil conditioner from dolomitic limestone and the Santa Ynez limestone quarry yielded building stone."

    Rock Products (in Los Angeles County)

    "In Los Angeles County the rock products industry ranks second to the mineral fuels industry both in value and quantity (circa 1953). The categories of rock products discussed in this section are (1) broken and crushed stone used primarily for riprap and fill in waterfront projects; (2) crushed stone (decomposed granite) used mostly for road base; (3) dimension stone, including flagstone, building stone, and facing stone; (4) miscellaneous rock products including diatomaceous shale, volcanic ash, and burned shale 'volcanic rock'; (5) sand, gravel, and crushed rock,* used primarily for concrete aggregate; (6) soapstone; and (7) specialty sands, including sand for foundry, locomotive, miscellaneous, and sandblasting uses. A complete listing of all rock products operations in the county may be found in the tabulated index.** (** Please note: This index is not included in this document.)

    (* Page 529 footnote: In technical usage 'stone' is the term applied to material that has been quarried from larger masses of rock, whereas 'rock' is applied to the material in place, before it is broken or cut. In this report, however, the widely accepted usage of the term 'crushed rock' is retained for crushed alluvial material used primarily for concrete aggregate.)

    "Appreciable tonnages in all categories are produced in Los Angeles County, the most notable being sand, gravel, and crushed rock. In 1950 the county yielded a total of 15,127,334 short tons of sand, gravel, and crushed rock valued at $9,835,428 (California Div. Mines, 1952a), nearly half of California's total commercial production (Chandler and Tucker, 1953, p. 1088).

    Broken and Crushed Stone (in Los Angeles County)

    "Broken and crushed stone, in blocks weighing as much as several tons, is now (circa 1953) quarried in three localities in Los Angeles County, two on Santa Catalina Island and the other in the Palos Verdes Hills. Large stone is used almost exclusively in harbor and waterfront construction where it is employed as riprap, ballast, dike core rock, and fill. Constant wave attack on sea front areas requires continuous maintenance of sea walls. Cyclopean concrete, in which stone blocks weighing 3 or 4 tons are surrounded by concrete grout, is also used for this purpose. Land in the harbor area, that has subsided as much as 10 or 15 feet, requires larger quantities of stone fill material from sources outside the sinking area. Smaller sizes of crushed stone and crusher-run base are used in large tonnages for road base.

    "Most outcrops of massive rock in Los Angeles County are too fractured and decomposed to be suitable sources of large stone. Granite rock has been quarried at several places in the San Gabriel Mountains for specific projects such as facing for flood control dams. Strong, undecomposed granitic rock, rarely procurable in the county in pieces weighing more than a ton or two, is brought in from Riverside and San Bernardino Counties when required. The principal sources of large stone in Los Angeles County is Santa Catalina Island. Barges bring stone to the mainland harbor from two active quarries on the island. Broken stone in smaller sizes is quarried at one site in the western Palos Verdes Hills (circa 1953).

    "Usual sizes of broken stone are (1) A-rock, a mixture of pieces weighing from 1 to 10 tons, but including pieces weighing as much as 30 or 35 tons when required; (2) B-rock, or riprap, as much as 2 tons in weight and at least 12 inches in diameter; (3) C-rock, from 6 to 12 inches in diameter; and (4) crusher-run base, less than 2 inches in diameter with all the fines. Modifications of these sizes are produced as required...."

    Crushed Stone (Decomposed Granite) (in Los Angeles County)

    "At several places in the county, crushed stone known as 'decomposed granite' ('DG') has been mined, primarily for use in road construction. Except for crushing, this material is not graded or processed before use. Most of the material mined is not actually granite, but sandy cobble conglomerate made up largely of granitic debris. The material is not suitable for use as sand, gravel, and crushed rock aggregate because of its decomposition and high clay content. Some variation in character of decomposed granite is acceptable, but too great a percentage of clay and fines makes the material unsatisfactory. Most of the material now produced is obtained in the Montebello Hills from the Pleistocene La Habra sandy conglomerate (Sheller, 1952) which overlies the upper Pliocene Pico formation and is as much as 500 feet thick (Stolz and Woodward, 1943, p. 336). One company mines decomposed Jurassic (?) granitic rock in the Santa Monica Mountains.

    "Mining is done by open-pit methods. Blasting is not required. Power shovels, bulldozers, and skip loaders load the material into crushing units that are commonly portable. Material is crushed by jaw crushers or hammer mills in closed circuit with vibrating screens. All material passing the screens, which usually have openings of about 1 ½ inches, is loaded by belt conveyor into storage bins or directly to trucks for haul to the job.

    "Only five operators are known to the writer to be producing decomposed granite commercially (circa 1953). Several hundred localities in the county have yielded decomposed granite in the past, being operated by contractors whenever necessary to procure materials for specific construction projects. The locations, status, and specifications for most of these deposits are listed with U. S. Army Engineers, California State Division of Highways engineers, and Los Angeles County Road Department engineers."

    Dimension Stone (in Los Angeles County)

    "The term 'dimension stone' is applied to blocks or slabs of natural stone, most of which are cut or broken to definite shapes or sizes (Runner and Jensen, 1951, p. 1134). In Los Angeles County three classes of dimension stone have been produced: flagstone, building stone, and facing stone. Flagstone and building stone are produced in minor amounts from rocks of the Pelona schist series in Bouquet and San Francisquito Canyons. Building stone, consisting of Upper Cretaceous sandstone of the Chico formation was produced in large tonnages in the Chatsworth area in the early 1900s. (Merrill, 1919, pp. 482-483). Large blocks from the Chatsworth quarries were used in the San Pedro Breakwater, and several churches, large buildings, and private residences were constructed from this stone. Several quarries were active but all were shut down by 1915 and no subsequent activity has been reported.

    "Small tonnages of sandstone and limestone have been produced for building stone in Santa Ynez Canyon in the Santa Monica Mountains.

    "Facing stone was produced prior to 1914 from talcose serpentine rock at the Banning quarry on Santa Catalina Island, and used for monumental, sanitary, and electrical purposes.

    "Other types of building stone that have been mined in Los Angeles County (Tucker, 1927b, pp. 330-332; Aubury, 1906, pp. 28, 128-131, 147, 154-155) include gneiss, granite, and trachyte, but little if any of these materials has been produced for many years. The general features of all of these dimension stone operations are summarized in the tabulated index of mining properties accompanying this report.*

    (* Please note that the tabulated index will not be included in this document, although some of the company information has been placed under the company name in the list of stone quarries in Los Angeles County.)

    "Flagstone and building stone have been produced from small quarries in the Bouquet Canyon and San Francisquito Canyon areas for many years. Flagstone is produced mainly in the San Francisquito Canyon, whereas the blockier pieces sold as building stone are obtained from a score or more of quarries widely dispersed in these areas. Much of the stone is used locally, but it is also distributed by dealers in the Los Angeles area for use in walls, gardens, and buildings.

    "The stone is obtained from gray quartz-mica-plagioclase schist and chlorite schist of the pre-Cambrian (?) Pelona schist series (Simpson, 1934, p. 380). In the quarry areas the schistosity ranges in strike from N. 45 E. to N. 65 E. and in dip from gentle to steep. Intricate contortion is uncommon. The schistosity plane is the only plane of pronounced fracturing. Thin slabs of large size are uncommon and careful hand splitting is required in nearly all quarries. These factors are the principal deterrents to expansion of the industry.

    "All the flagstone and building stone quarries are small open-pit operations. Quarries are usually in steep hillsides where the schist is well exposed and relatively uncontorted. Blasting and bulldozing expose suitable faces. Slabs and blocks are broken out and split by hand with the aid of crowbars and hammers and chisels. Pieces are then loaded onto trucks and hauled away for sale. The largest quarries visited by the writer have each yielded about a thousand tons of commercial rock.

    "Several quarries are on placer claims, but most operations are on National Forest land withdrawn from mineral entry. Special use permits are granted for removal of stone from such areas. If the rock is to be sold, a fee of 25 cents per ton produced is paid to the Forest Service. If the rock is to be used by the operator for private projects, no matter where, no fee is charged." (circa 1953)

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