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San Diego County Stone Industry (Continued)

  • San Diego County – the Dimension Stone Industry of San Diego County and San Diego County Commercial “Black Granite.” The following excerpts are from Commercial 'Black Granite' of San Diego County, California, Special Report 3, by Richard A. Hoppin and L. A. Norman, Jr., State of California, Department of Natural Resources, Division of Mines, San Francisco, December 1950. (Used with permission, California Department of Conservation, California Geological Survey.)

    "Dimension Stone Industry of San Diego County – Geography and General Geology of the Granite-producing Areas.

    The granite quarries of San Diego County lie within the Peninsular Range province. The Peninsular Range province includes those parts of Baja California and Southern California that lie south of the San Gabriel and San Bernardino Mountains, west of the Salton Imperial depression, and east of the Pacific coastal plain. Most of the province is hilly or mountainous, and many of the individual mountain masses along the eastern boundary of the province are 5,000 to 10,000 feet high. In the lower granite-producing areas farther west, the general relief is approximately 1,500 feet.

    Figure 1. Index map of San Diego County granite quarries (monumental and building stone). Index map of San Diego County granite quarries

    "Except where recently burned over, the hills are covered with a thick growth of brush. Where underlain by gabbroic rocks, or 'black granite,' these hills are mantled with reddish-brown soil. Many of the more silicic rocks, in contrast, form rough, boulder-strewn ridges and slopes.

    "The rainfall in the lower, westerly parts of the province averages about 15 inches, and occurs mainly during the period December-April. The winters are mild and the summers characteristically hot and dry; the climate ordinarily permits operation of the quarries on a year-round basis.

    "A large part of the Peninsular Range country is underlain by intrusive igneous rocks of probably Upper Cretaceous age. (1) These rocks represent a great, complex batholith, and were intruded into Mesozoic schists, quartzites, and volcanic rocks along the eastern border of the province. Like the province as a whole, the batholith is elongated in a southeasterly direction. The intrusive rocks are exposed continuously from Riverside, California, to points many miles south of the Mexican border, a distance of more than 100 miles within the state of California. The average width of the batholith is about 60 miles. Its western margin is in part overlapped by the younger sedimentary rocks.

    "The black granite' quarries in San Diego County are in large intrusive masses of San Marcos gabbro, which is the oldest of the major rock types in the batholith. (2) This gabbro, or black granite, forms numerous stock-like bodies that in many places are entirely or partly surrounded by larger, younger masses of tonalite and granodiorite. The largest exposure of black granite in the area extends over about 11 square miles; others cover 5 square miles or less.

    (1) Page 6, footnote 1: Larsen, E. S., Jr., Batholith and associated rocks of Corona, Elsinore and San Luis Rey quadrangles, Southern California; Geol. Soc. America Mem. 29, 182 pp., 1948.

    (2) Page 6, footnote 2: Miller, F. S., Petrology of the San Marcos gabbro, southern California: Geol. Soc. Am. Bull., vol. 48, pp. 1397-1426, 1937.

    Historical Sketch (of the San Diego County Granite Industry)

    "The granite industry in San Diego County evolved from local use of the stone by early settlers. Recorded production of granite as a dimension stone dates from 1898, although granite quarries were operated several years earlier. Large tonnages of rubble and riprap were produced for breakwater and dam construction during the years near the turn of the century. This bulk us of granite has continued to the present, but during recent years has become distinct from dimension stone uses.

    "Production of paving blocks cut from granite was first reported in 1910, and during succeeding years a small but flourishing industry was supported by the demands of railroads for rail-lining material in urban areas. Proficient stonecutters, many of them trained in the European countries of their birth, produced blocks by hand methods at numerous quarries in the Grossmont, Santee, and Foster areas. Some of these old quarries are visible in the low hills half a mile south of Santee and along the west side of the lake-side Ramona highway, a few miles north of Lakeside. An important factor in these quarrying activities was the proximity of the San Diego, Cuyamaca and Eastern Railway, now abandoned.

    "Dimension stone for building and memorial purposes found a gradually increasing market, partly as a result of wider recognition of the quality of the stone, and partly because of sales efforts by quarrymen, who were in search of a new market to replace declining demands for riprap and paving stone. James Simpson of the Simpson-Pirnie Granite Company, San Diego, was one of the pioneers in the stone business, operating quarries at Santee and Foster from 1888 to 1932. The company reported sales of building stone, monumental stone, paving blocks, rubble and riprap. This diversified production probably accounts in large part for their 46-year period of operation, longest of any in the county. Dimension stone for use in the construction of government buildings at Fort Rosecrans, on Point Loma near San Diego, was quarried in the Foster area by the Waterman Granite Company in 1903-04. (3)

    (3) Page 6, footnote 3: Aubury, Lewis E., The structural and industrial materials of California: California Min. Bur. Bull. 38, p. 52, 1906.

    "All of this early work was done in a region of predominantly light-gray granodioritic rock; it was not until 1921 that the currently important black granite (gabbro) was exploited extensively, although Jose Cova produced small amounts of the stone before 1921 from a quarry near Santee. In 1921 the Blye Stone Company, Los Angeles, and W. E. Van Deventer reported sales of such material from two quarries near Bernardo. In 1922 Robert J. Magee reported black granite production from his quarry northeast of Pala, in the northern part of the county. About the same time, the area southwest of Escondido was opened up; it is now a major source of stone. First production from the San Marcos-Vista area was in 1938. John Stridsburg, present operator of the Crystal Black granite quarry, has been active in the Escondido area since 1923, and has reported continuous production under his own name since 1926.

    "All quarries and producers listed in the records of the State Division of Mines are shown in table 1. Many other companies and individuals, including those failing to submit production records, those producing granite products other than monumental and building stone, and the many stone workers, are not listed but nevertheless played an important part in the development of the county's granite industry.

    Location of Quarries and Producers (in San Diego County)

    "The granite quarries of San Diego county are shown in figure 1. There are three principal centers of production, all in the western half of the county. Light-gray granodiorite is obtained from an area within a 5-mile radius of Lakeside, whereas most of the black granite is obtained from two areas, one within a 5-mile radius of Escondido and the other within a 3-mile strip that lies 4 miles east of Vista. The confinement of quarrying activity to these areas probably is due partly to their position with respect to transportation, as well as to the wise tendency to continue operations in a known area of good stone. Undoubtedly there are other deposits of satisfactory stone that could be exploited if the demand were sufficient.

    "The list of producers in table 1 shows clearly the high mortality rate of producers in terms of length of operations. Of the seven 1948 producers, only two reported production prior to 1937. Also of interest are the numerous trade names applied to the stone that has been marketed. One of them, 'Black Diamond Granite', is registered and copyrighted with the U. S. Patent Office. The 16 different names noted in table 1 form only a part of the complete list, no accurate record of which is available.

    Table 1. San Diego County Granite Producers of Building and Monumental Stone. San Diego County Granite Producers of Building and Monumental Stone.

    Technology (Quarrying Technology in San Diego County)

    "Hardness, texture, and other properties that substantially affect the suitability of granite as a dimension stone also creates many problems in quarrying and preparation. Techniques developed for quarrying softer types of dimension stone are not always applicable to operations in granitic rocks, where production costs are often relatively high. Quarrying and finishing methods have been well described by Bowles (4) in his comprehensive study of the stone industries.

    (4) Page 7, footnote 1: Bowles, Oliver, The stone industries, McGraw-Hill Book Company, 2d ed., pp. 143-167, 1939.

    "The granite quarries of San Diego County are small to moderate in size, and are of two distinct types. In general, the black granite quarries have been in deposits of residual boulders, whereas most granodiorite quarries have been operated in ledge, or massive rock. Both types of quarries are commonly started as shelf excavations, with the development of an opening horizontally into the hillside. Black granite quarries ordinarily have been continued as 'shelf quarries,' but some of them and most of the granodiorite quarries have been deepened into 'pit quarries,' in which the rock is obtained from points below the original quarry floor.

    "After exposure in the quarries, boulders are split by drilling and blasting. the split portions of the boulders then are worked into smaller blocks by the 'plug and feather' method (fig. 2). In granodiorite quarries, maximum advantage is taken from the joint sets to obtain large sized quarry blocks from which smaller ones are made.

    Figure 2. Boulder of black granite being worked in quarry. Emil Johnson and Sons quarry, Vista. Boulder of black granite being worked in quarry

    "Equipment used in the quarries consists of the usual stoneworkers' hand tools, pneumatic hand drills, portable compressors, single derricks, and in some places, a bulldozer to move waste material. Only one quarry is equipped with an electrically-powered steel derrick and gang saw. The saw is used to produce slabs of various thicknesses (figs. 3 and 4).

    Figure 3. Gang saw with partly completed cuts in black granite boulder. Pacific Cut Stone and Granite Company quarry, Escondido. Gang saw with partly completed cuts in black granite boulder.
    Figure 4. View of quarry with residual boulders in place and stockpiles for gang saw processing. Sawed slabs in foreground. Pacific Cut Stone and Granite Company quarry, Escondido. View of quarry with residual boulders in place and stockpiles for gang saw processing

    "Disposition of waste in quarry operations in quarrying operations is always an important problem. Operators of quarries in black granite must handle both waste rock and the disintegrated material that surrounds the boulders. The latter is used to maintain quarry floors, and at one place is also sold as surfacing material for driveways and roads. Many of the older granodiorite quarries, as judged from present appearance, were literally 'worked into a hole,' with poorly planned development of steep or overhanging walls on one or more sides, excavations of awkward shape, and with rapid accumulation of waste for which satisfactory disposition was not provided.

    "The quarrying methods typically used in San Diego County appear crude and inefficient as compared with those of other areas, particularly the important granite centers of the eastern United States. The local quarries, however, present difficult and unusual problems. Many excellent techniques ordinarily used in the quarrying of massive rock are not feasible for residual boulder deposits. All known techniques should be studied and considered, however, as many of these might be useful, and might lead to reduction of operating costs.

    "The physical characteristics of granite contribute to problems of finishing, as well as quarrying the stone. No finishing shops are located on quarry premises in the county, although two of the producers active in 1948 maintain such shops elsewhere. These and other finishing shops in the county use essentially standard methods and equipment as described by Bowles. (5) Location of shops at or near quarries, adoption of improved methods and equipment and attention to the possibilities of production-line methods might contribute to lower costs.

    (5) Page 8, footnote 1: Bowles, Oliver, The stone industries, McGraw-Hill Book Company, 2d ed., pp. 156-167, 1939.

    Production and Economic Conditions (of Granite in San Diego County)

    "Production of building and monumental granite in San Diego County during the 51-year period 1898-1948 has amounted to 577,276 cubic feet valued at $1,344,273, or 5.8 percent of the total California production for that period. In 1948 the county production constituted about 30 percent of the total state production. The output of the county's industry has fluctuated greatly, with trends generally parallel with those of the state's industry. California' greatest output, in terms of value, was reached in the years 1921-30, an active period for the San Diego County industry as well. This was due mainly to the accelerated building activity of the period. The record year in state production, 1925, was second highest for the county, whose maximum output was reached in 1947.

    "As shown in tables 1 and 2, general business conditions are reflected in the granite production figures for both California and San Diego County. Financial depressions, labor troubles, building booms, and periods of prosperity have shown their effects during the years. (6) The panic of 1907, for example, had little effect upon state production, but a marked effect upon county production which dropped sharply in 1908. The financial depression before World War I, in contrast, resulted in a lowering of both state and county production. Although the county production improved in 1915 over the 1914 low, the state production did not owing in part to a strike of stonecutters. (7)

    (6) Page 8, footnote 2: Bowles, Oliver, and Hatmaker, Paul, Trends in the production and uses of granite as dimension stone: U. S. Bur. Mines Rept,. of Inv. 3065, 1935. Data on national economic conditions as related to the granite industry, as well summarized in this paper, have been used by the authors for comparison with California and San Diego County Production.

    (7) Page 8, footnote 3: Bradley, Walter W., California mineral production for 1915, California Min. Bur. Bull. 71, p. 58, 1916.

    "The period 1916-18, with its labor troubles, short labor supply, higher operating costs, and other wartime conditions, was a serious one for both the national and the California stone industry. The state's 1918 production of $139,861 was its lowest since 1888. County production during the same period was at a low level. The years 1921 and 1922, in which many post-war economic adjustments were made, marked the start of California's most important years of production, and likewise a corresponding period of prosperity for the industry in San Diego County. Increased building activity, particularly the construction of public buildings in the Los Angeles area, was directly responsible for the high output of dimension granite in 1924-25. (8) Monumental use, which normally requires that a stone take a smooth polish, demands rock of the highest quality, as texture, color, and physical defects are easily seen in the polished stone.

    (8) Page 9, footnote 1: Bradley, Walter W., California mineral production for 1925: California Min. Bur. Bull. 97, p. 70, 1926.

    "Both Granodiorite and black granite are in constant demand for monumental purposes. The popularity of black granite is indicated by production figures from 1921, when the rock was first extensively quarried. From 1921 to 1948 the output of this rock constituted 51 percent of the total production of dimension stone in the county. For the entire 51-year period, 1898-1948, it constituted 43 percent of the total, and for the last five years, 1944-48, it amounted to about 90 percent. Monuments made from this stone are sold not only throughout California, but in many other states, Canada, Mexico, and the Hawaiian Islands.

    "The recently completed Flagpole Memorial, at the Nevada entrance to Hoover Dam, is made from the black granite. As a building stone, this rock is used extensively in veneers and facings, alone or incorporated with other natural stone, or with manufactured synthetic building materials, Its dark color and uniform texture provide a pleasing accent, and harmonize well with other materials. Moreover, the stone is easily maintained after installation.

    Table 2. Production of building and monumental granite 1898-1948. Production of building and monumental granite 1898-1948.

    "The recently completed General Petroleum Building in Los Angeles (fig. 5) illustrates the use of San Diego black granite in combination with terra cotta. A few of the many other buildings in which this stone has been used are the Mirror Building, Western Union Building, Broadway Crenshaw, Saks 5th Avenue, and Bullock's Pasadena in the Los Angeles area, and the Appraisers Building and Hastings Building in San Francisco. Its use in the Minnesota Mining and Manufacturing Company Building, St. Paul, Minnesota, Salvation Army Building, Detroit, Michigan, and in the United States Embassy Building, Havana, Cuba, reflects its widespread distribution outside the state.

    Figure 5. General Petroleum Building, Los Angeles. San Diego County black granite used on lower part of building and terra cotta on upper section. General Petroleum Building, Los Angeles

    "Light-gray granite of the county, used so extensively in earlier years for construction purposes, also has found great favor as a monumental stone. Its even texture and 'silver-gray' color make it suitable for many purposes. Unfortunately, production of this rock has dropped to a negligible amount during recent years, and its once well-established position is threatened by lack of supply. Both producers and finishing shops have indicated that there has not been sufficient available stock to fill recent demands...."

    Geological Studies of Selected Quarries - Introduction (San Diego County)

    "Seven operating quarries were studied during the spring of 1943. Six of these quarries have been developed in the San Marcos gabbro, or black granite, and the seventh is in granodiorite. The quarries examined are the John Strisburg, Pacific Cut Stone and Granite Company, and the Valley Granite Company near Escondido; Pete Matson at Vista; Emil Johnson and Sons at Pala and at Vista; Emil Johnson and Sons at Pala and at Vista; and the Cameron-Deering at Lakeside. The location of these quarries is shown on the index map (fig. 1).

    Figure 6. Monument made of San Diego County granodiorite. Monument made of San Diego County granodiorite.
    Figure 8. Monument carved from San Diego black granite (gabbro). Monument carved from San Diego black granite (gabbro).

    "Residual boulders are being worked in all the black granite quarries except the Stridsburg. These boulders are remnants of fresh rock surrounded by crumbly, decomposed material. The massive granite is traversed by a network of joint, fracture, and sheeting surfaces that divides the rock into blocks of various sizes. The water descending through the narrow openings along these surfaces contains a small amount of carbonic and sulphuric acids. Because the minerals of the granite crystallized at higher temperatures than exist in this surface environment, they are susceptible to alteration by these cold, dilute acidic solutions. Decomposition and disintegration take place, moving inward from all sides of each fracture-bounded block and gradually rounding its corners until only a boulder is left. This results in a concentric laying that has been called onionskin structure (fig. 9). The remaining boulders range from a few inches to 30 feet in diameter...."

    Figure 7. Graphs showing California and San Diego County granite production. Curves are broken to conceal production of single producers for period. Graphs showing California and San Diego County granite production.
    Figure 9. Residual boulders in granular matrix. Emil Johnson and Sons quarry, Vista. Residual boulders in granular matrix. Emil Johnson and Sons quarry, Vista.
    Figure 10. Transported boulders, Emil Johnson and Sons quarry, Pala. Transported boulders, Emil Johnson and Sons quarry, Pala.

    Petrology - Introduction (San Diego County)

    "A complete account of the geology of the batholith of southern California was recently published by Larsen. (9) Miller has made a thorough study of the petrography and petrology of the San Marcos gabbro. (10)...."

    "The commercial designation 'black granite' is used here for the gabbroic rocks. More specific petrographic names are employed if a specific rock type is discussed."

    (9) Page 13, footnote 1: Larsen, E. S., Jr., Batholith and associated rocks of Corona, Elsinore and San Luis Rey quadrangles, southern California; Geol. Soc. America Mem. 29, 182 pp., 1948.

    (10) Page 13, footnote 2: Miller, F. S., Petrology of the San Marcos gabbro, southern California: Geol. Soc. Am. Bull., vol. 48, pp. 1397-1426, 1937. Miller, F. S., Hornblendes and primary structures of the San Marcos gabbro: Geol. Soc. Am. Bull., vol. 49, pp. 1213-1232, 1938.

    Staining of Monuments in San Diego Cemeteries

    "Owing to stains developed on black-granite monuments in several San Diego cemeteries, the use of this stone was for a time considerably curtailed. A study of these monuments was made to determine whether the staining actually is greater on the black granite than on other stones, or whether it appears to be greater because of the darker color of the rock.

    "The staining was found to be of two types: (1) a brown stain formed by oxidation of ferromagnesian silicates and iron sulphide minerals in the rock, and (2) a white coating of extremely fine-grained material that does not appear to be the result of oxidation...."

    Figure. 17. Disfiguration of black granite monument. White coating has been scraped from surface to show original dark color of polished stone. Disfiguration of black granite monument.
    Figure 18. Disfiguration accentuated on carved surface of monument. Disfiguration accentuated on carved surface of monument.
    Figure 9. Residual boulders in granular matrix. Emil Johnson and Sons quarry, Vista. Residual boulders in granular matrix. Emil Johnson and Sons quarry, Vista.
    Figure 10. Transported boulders, Emil Johnson and Sons quarry, Pala. Transported boulders, Emil Johnson and Sons quarry, Pala.
    Figure 11. Sheet structure at Simpson quarry, Santee. Sheet structure at Simpson quarry, Santee.

    Figure 12. Partly weathered rock traversed by numerous fractures. Emil Johnson and Sons quarry, Vista.

    Partly weathered rock traversed by numerous fractures. Emil Johnson and Sons quarry, Vista.
    Figure 13. View into Cameron-Deering quarry, Lakeside. Distribution of the many fractures in the rock is such that uniform blocks are difficult to obtain. View into Cameron-Deering quarry, Lakeside.
    Figure 14. Perfect joint plane. Cameron-Deering quarry, Lakeside. Perfect joint plane. Cameron-Deering quarry, Lakeside.
    Figure 15. Valley Granite Company quarry, Escondido. General view of quarry workings. Valley Granite Company quarry, Escondido. General view of quarry workings.
    Figure 16. Vertical west face of McGee quarry, near Pala, as it appeared in July 1947. Note large boulders in upper part of thick-well-defined "creep" layer, which also contains smaller boulders that show some exfoliation. The underlying residual material, with its large, spheroidally weathered boulders, is well exposed to the right of the man. Its sharp upper contact is elsewhere concealed by slumped debris and quarry waste. Prepared from a sketch by R. H. Jahns. Vertical west face of McGee quarry, near Pala, as it appeared in July 1947.

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