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San Diego - List of Stone Quarries, Etc.*

(* Please note this list does not include sand, gravel, or decomposed granite quarries.)

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  • Dos Cabezas (north of), San Diego County, California – Dos Cabezas Limestone Deposits (Limestone & Marble) (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.)

    "Dos Cabezas limestone deposits are in secs. 22, 23, 26, 27, T. 16 S., R. 8 E., S. B., about 1 ½ miles north of Dos Cabezas siding on the San Diego & Arizona Railroad.

    "Beds of white crystalline limestone varying in thickness from 20 to 100 feet (Tucker 25c, p. 370)* are said to extend at intervals for a length of 1 mile with a strike of N. 30 W. and over a width of three-quarters of a mile. The limestone has been intruded by granitic rock and has some schist layers. It has been changed to marble of fine grain in some layers but the largest outcrop is a coarsely crystalline white limestone reported to carry 98 percent CaCO3, and occurring on a hill 800 feet high. These deposits are idle and undeveloped, so far as known."

    (* W. Burling Tucker, "Los Angeles field division, San Diego County," California Min. Bur. Rept. 21, pp. 325-382, ills., 1925)

    • Dos Cabezas, San Diego County, California – the Dos Cabezas Deposit (Limestone) & Dos Cabezas Marble Placer Claim (Marble)  (from Geology and Mineral Resources of San Diego County, County Report 3, by F. Harold Weber, Jr., Geologist, California Division of Mines and Geology, 1963, pp. 182.  (Used with permission)  (This book is available on the Internet Archive – Texts.)

      Dos Cabezas Deposit  (pp. 182):  (Remarks and references)  “See Heathman deposit in text.  (Logan 47:301; Tucker 25:370).”  (To see the bibliography that lists the books cited in the previous sentence, see the “Annotated Bibliographies” section of Geology and Mineral Resources of San Diego County, pp. 283-309.)

      Dos Cabezas Marble Placer Claim  (pp. 182):  (Remarks and references)  “One of the claims that cover the Golden State deposit, which see in text.  (Tucker and Reed 39: pl. 1).”  (To see the bibliography that lists the books cited in the previous sentence, see the “Annotated Bibliographies” section of Geology and Mineral Resources of San Diego County, pp. 283-309.)

    • Dos Cabezas Limestone/Marble Deposit

      Also see:  “Dos Cabezas Springs (northeast of), San Diego County, California – Golden State Mining and Marble Company Marble Deposits (Marble)” et al. below. 

  • Dos Cabezas (north of), California – Elliott Dolomite Property (Dolomite) (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.)

    "Elliott dolomite property comprises two 160-acre association placer claims in the S ½ sec. 26 and adjacent parts of secs. 27, 34 and 35, T. 15 S., R. 8 E., S. B. The nearest loading station on San Diego & Arizona Railroad is 8 miles south. Mrs. Ellen Elliott Chilwell, Live Oak Springs via Pine Valley Post Office, California, Fred Elliott, Boulevard Post Office, California and others, are owners.

    "The deposit traverses a mountain 1500 feet high, a quarter of a mile wide and about a mile long, in the desert near the Imperial County line.

    "The following analysis was made by Smith Emery & Company, Los Angeles (No. 188685):"

    Silica SiO2, 0.43 percent
    Iron oxide Fe2O3, 0.10 percent
    Aluminum oxide Al2O3, 0.25 percent
    Calcium oxide CaO, 31.37 percent
    Magnesium oxide MgO, 20.89 percent
    Carbon dioxide CO2, 46.70 percent
    Sulfuric anhydride SO3, none
    Phosphoric anhydride P2O5, trace
    Acid insoluble matter, 0.83 percent
    Purity as calcium-magnesium carbonate, 98.8 percent

    • Dos Cabezas (north of), California – the Elliot Deposit (Limestone)  (from Geology and Mineral Resources of San Diego County, County Report 3, by F. Harold Weber, Jr., Geologist, California Division of Mines and Geology, 1963, pp. 182.  (Used with permission)  (This book is available on the Internet Archive – Texts.)

      (pp. 174)

      “The only deposit of dolomite in the county that has been described is the Elliott Deposit, near the eastern boundary of the county, on the south slope of the Coyote Mountains (see description below).  This deposit was worked briefly as a source of roofing granules in the early 1950’s….” 

      Elliot Deposit (dolomite)

      Location:  Secs. 26, 27, 34, and 35, T. 15 S. R. 8 E. S.B.M.; about 5 ½ miles north of Dos Cabezas, on the south flank of the western part of the Coyote Mountains.

      Ownership:  Fred M. Elliot, c/o Mac’s Store, Manzanita, Pine Valley Post Office; Rena Rath Elliot, 433 Juniper Street, San Diego 1; and James Elliot, San Diego, own two unpatented association placer claims which covers 320 acres (1957).

      “The Elliot family located the White Dolomite Numbers 1 and 2 Claims in 1924.  These claims comprise the W. ½ W. ½ SE. ¼, S. ½ N. ½ SW. ¼, and the S ½ SW. ¼ Sec. 26; the SE. ¼ SE. ¼ Sec. 27; the NE. ¼ NE. ¼ Sec. 34; and the N. ½ NW. ¼ Sec. 35 (Fig. 40.)  The deposit has been worked only briefly, during 1952-1953, as a source of roofing rock.  It is within Anza-Borrego Desert State Park.

      “Figure 40.  Map showing unpatented property holdings that cover the Elliot dolomite deposit, Coyote Mountains.”  (pp. 174) Map showing unpatented property holdings that cover the Elliot dolomite deposit, Coyote Mountains, San Diego Co., CA

      “The Elliot property covers part of a body of preCretaceous metamorphic rocks which underlies the southwest side of the western part of the Coyote Mountains.  The rocks consist mainly of interlayered biotite schist and crystalline dolomite which are cut by pegmatite dikes.  The Elliot workings develop a layer of dolomite that is perhaps several hundred feet thick, and at least several hundred feet long, which strike east-northeastward and dips about 40º to the northwest.  The dolomite contains a small proportion of thin layers of biotite schist.  In the workings the dolomite is generally milky-white, although impure strata contain contact minerals such as red-brown garnet and green diopside.  Where the dolomite has been mined, its texture is medium- to coarse-grained.

      “Following is an analysis of a sample from the Elliot Deposit collected by O. E. Bowen, Jr., of the Division of Mines and Geology and analyzed by Abbott Hanks, Inc., San Francisco in June 1955:  SiO2, 0.26 percent; Fe3O4, 0.09 percent; Al2O3, 0.15 percent; CaO, 31.08 percent; MgO, 20.71 percent; and P2O5, 0.06 percent.  In addition to roofing rock this material might be used as a refractory, as agricultural dolomite, concrete aggregate, ballast, road metal, or road base.

      “Principal development is an oval, bench-like cut about 10 to 20 feet wide, 10 to 20 feet high and 30 to 40 feet long, low on the steep southern slope of the Coyote Mountains (Photo 47).  During 1951, the Milroy Roofing Company, of south Gate, worked the deposit for about six months in an attempt to produce roofing rock.  Several thousand tons of dolomite was quarried which consisted mainly of talus composed of angular fragments of white dolomite as large as 10 feet in diameter.  In March 1957 only a small shack and a loading bin remained on the property.

      “Photo 47.  View northwest toward workings in Elliot dolomite deposit, which is low on south side of Coyote Mountains.”  (pp. 175) View northwest toward workings in Elliot dolomite deposit, which is low on south side of Coyote Mountains, San Diego Co., CA

      (pp. 182)

      (Map No.)  294;  (Name of claim, mine, or group)  Elliot deposit; (Location)  Southeastern part of county; (Owner name, address)  (blank); (Geology)  (blank).

      (Remarks and references)  “See text.  (Logan 47:301).”  (To see the bibliography that lists the books cited in the previous sentence, see the “Annotated Bibliographies” section of Geology and Mineral Resources of San Diego County, pp. 283-309.)

  • Dos Cabezas Springs (northeast of), San Diego County, California – Golden State Mining and Marble Company Marble Deposits (Marble) (Excerpt 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 V. "The Counties of San Diego, Imperial," by Frederick J. H. Merrill, Ph.D., Field Assistant (field work in December, 1914), California State Mining Bureau, San Francisco, California, 1916, pp. 427-634.)

    "About 4 ½ miles northeast of Dos Cabezas Springs, Sec. 21, T. 16 S., R. 8 E., are two claims covering a deposit containing two colors of marble, and belonging to the Golden State Mining and Marble Company, C. A. Walker, president, Watts Building, San Diego. One stratum, extending about 600 feet in length and 20 feet in width, is pure white, interspersed with tiny black dots. This marble is of high grade, fine grained, slightly harder than common marble and takes a high polish. Adjoining this stratum is one of light gray blue over 600 feet in length and about 180 feet in width. This is of the same quality as the white and black dotted, and is well suited for interior decoration, as in corridors and panels. This deposit lies about 1 mile from the San Diego and Arizona Railroad, but must await the completion of that line."

    • San Diego County, California – Golden State Marble Deposits (Marble) (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.)

      "Golden State marble deposits were located years ago by a company of this name in sec. 21, T. 16 S., R. 8 E., S.B., within a mile of the line of the San Diego and Arizona Railroad. A bed of white marble outcrops 600 feet in length by 20 feet in width (Merrill 16a, p. 674)* and a gray-blue bed has a width of 180 feet and length of 600 feet.

      "The company once had larger holdings of marble a few miles east in Imperial County, but never developed any of its deposits."

      (* Frederick J. H. Merrill, "Imperial County," California Div. Mines Rept. 14, pp. 637-722, illus., 1916 )

    • Dos Cabezas Area, San Diego County, California – the Golden State (Dos Cabezas Marble Placer) Deposit (Limestone/Marble)  (from Geology and Mineral Resources of San Diego County, County Report 3, by F. Harold Weber, Jr., Geologist, California Division of Mines and Geology, 1963, pp. 182.  (Used with permission)  (This book is available on the Internet Archive – Texts.)

      (pp. 175, 177)

      Golden State (Dos Cabezas Marble Placer) Deposit

      Location:  W. ½ Sec. 23, T. 16 S., R. 8 E., S.B.M.; in the southeastern part of the county, about one mile northeast of Dos Cabezas.  Within Anza-Borrego Desert State Park.  Ownership:  B. A. Sweet, Pine Tree Portland Cement Company, Escondido, owns all but a small part of two northeast-trending, essentially end-to-end patented claims which cover 37.97 acres, name in the middle of the W. ½ Sec. 23 (Fig. 41).  Small parts of the claims are held by C. I. Smith and others, c/o 408 A Rodriguez, Watsonville (1957).

      “Figure 41.  Map showing patented claims that cover part of the Golden State crystalline limestone deposit, near Dos Cabezos.”  (pp. 175) Map showing patented claims that cover part of the Golden State crystalline limestone deposit, near Dos Cabezos.” San Diego Co., CA

      “The Golden State Deposit was probably first prospected in the 1920’s, and was worked most recently about 1950, as a source of crushed stone for use as roofing granules.  The present owner leased the property in 1957 with Ed Roberts of San Diego, and purchased it in 1957.  He contemplated using the deposit as a source of limestone for a proposed cement plant in southeastern San Diego County or southwestern Imperial County.  In May, 1960 the property was idle and there was no equipment on it.

      “The Golden State property lies in the northeastern part of the area that encloses the Dos Cabezas Limestone Deposits, as shown in Photo 46 and Fig. 42.  The rocks in the northeastern part of the area consist chiefly of interlayered biotite schist, subordinate crystalline carbonate rocks, and minor quartzite which are intruded widely, but irregularly, by diorite.  Cretaceous quartz diorite, and dikes of granite pegmatite.  The Golden State property contains the largest body of carbonate rocks in the district.  This body, which consists of limestone and subordinate magnesian limestone, is exposed along the south slope of a north- to northwest-trending ridge which dominates the middle of Section 23 (Photo 48).  The body is very crudely hourglass-like in plan, with its long axis trending east along the ridge slope.  The bedding of the deposit strikes east-northeastward and dips 50º -80º northwest, into the slope.  The body is about 900 feet long, and ranges in thickness from about 75 to 450 feet.  It is bordered on the east by quartz diorite, on the north by quartz diorite and diorite, and on the south and west by alluvium. Additional, smaller carbonate bodies enclosed by quartz diorite lie to the northeast of the main body.

      “Figure 42.  Generalized Geologic Map of the dos Cabezas Limestone Deposits, San Diego County, California.”  (pp. 176) “Figure 42. Generalized Geologic Map of the dos Cabezas Limestone Deposits, San Diego County, California.”
      “Photo 48.  View north-northwest, showing Golden State crystalline limestone deposit.  Limestone underlies southeastern slopes of prominent hill, which is about a mile north of Dos Cabezos.  The cut in the middleground is about 135 feet long.”  (pp. 177) “Photo 48. View north-northwest, showing Golden State crystalline limestone deposit. Limestone underlies southeastern slopes of prominent hill, which is about a mile north of Dos Cabezos. The cut in the middleground is about 135 feet long.” (pp. 177

      “About 600 feet southwest of the main body, in the most southwesterly part of the property, is a low, isolated outcrop which consists of carbonate bodies interlayered with other metamorphic rocks.  The largest of these bodies is about 250 feet long and 150 feet in maximum width.

      “Limestone and magnesian limestone of the Golden State property are thinly to thickly bedded and are very resistant to erosion.  Rocks of limestone composition are fine- to very coarse-grained and range in color from white to pale gray.  The gray color is most commonly caused by graphite which is disseminated sparsely and finely through the calcite.  Some limestone beds contain thin, dark-gray bands which are composed of a relatively large proportion of graphite with calcite; less common are pale orange bands which are composed of finely disseminated garnet in calcite.  Rocks of magnesian limestone composition generally are fine- to medium-grained and cream-colored.  A sample that was taken by the writer across the widest part of the main carbonate body contained the following percentages of its principal constituents (analysis by Twining Laboratories, Fresno, June 1960):  CaO, 46.51 percent; MgO, 7.35 percent; SiO2, 3.27 percent; Al2O3, 0.79 percent; Fe2O3, 0.19 percent; and P2O5, 0.29 percent.

      “The principal workings of the property consist of two shallow cuts at the southern edge of the main body.  These cuts have a combined length of about 210 feet.  The oldest working on the property is a small, shallow cut at the western part of the north edge of the main body.  Additional workings consist of a few minor cuts and pits in the most southwesterly deposits.

      “The main body of the Golden State property comprises the principal reserves of carbonate rocks in the district.  Relatively large tonnages of this body could be mined by open pit methods, and it is assumed that limestone of the same composition extends down the dip of the body, and probably beneath the alluvium which lies to the west and south.”

      (pp. 182)

      (Map No.)  295;  (Name of claim, mine, or group)  Golden State (Dos Cabezas Marble Placer) deposit; (Location)  Dos Cabezas area; (Owner name, address)  (blank); (Geology)  (blank).

      (Remarks and references)  “See text.  (Logan 47:301; Merrill 14:674; Tucker and Reed 39: pl. 1).”  (To see the bibliography that lists the books cited in the previous sentence, see the “Annotated Bibliographies” section of Geology and Mineral Resources of San Diego County, pp. 283-309.)

  • Dos Cabezas (north of), San Diego County, California – Heathman Limestone Quarry (Limestone) (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.)

    "Heathman quarry, R. W. Heathman, owner, San Diego (in 1939), is in sec. 27, T. 16 S., R. 8 E., S.B., 1 mile north of Dos Cabezas siding. Thirty tons of white limestone was mined by open pit in 1939 from a deposit 10 feet wide."

    • Dos Cabezas Area, San Diego County, California – the Heathman (Dos Cabezas, Heathman Quarry, Mamie Heathman) Deposit (Limestone)  (from Geology and Mineral Resources of San Diego County, County Report 3, by F. Harold Weber, Jr., Geologist, California Division of Mines and Geology, 1963, pp. 182.  (Used with permission)  (This book is available on the Internet Archive – Texts.)

      (pp. 177-178)

      Heathman (“Dos Cabezas, Heathman Quarry, Mamie-Heathman) Deposit

      Location:  NE. ¼ Sec. 27, T. 16 S., R. 8 E., S.B.M.; southeast part of the county, about ¼ to ½ mile north of Dos Cabezas siding of the San Diego and Arizona Eastern Railroad; now within Anza-Borrego Desert State Park.  Ownership:  Charles Dunston, Dulzura, owns one 160-acre unpatented association placer claim (1958).

      “The limestone deposits in the Dos Cabezas area were described first in 1925 by W. B. Tucker (1925, p. 370) who reported that 480 acres in Sections 22, 23, 26, and 27 were claimed by M. A. Turner and Associates of San Diego.  R. W. Heathman (stepfather of the present owner) and others, relocated the NE. ¼ of Section 27 in 1924.  The property remained idle until 1950 when it was leased to the Campo Milling Corporation which processed limestone mined form this deposit in the Pacific Mill at Campo (see also Pacific Deposit, under ‘Feldspar’).  This company produced roofing granules, chicken grit, and agricultural limestone for two or three years.

      “Most recently the property was leased to Don Weaver, of Jacumba, who mined about 5,000 tons of limestone from it.  Most of this material was crushed, screened and bagged adjacent to the railroad at Dos Cabezas (Photo 49).  About two-thirds of the material mined was ground to minus 1/8 inch, plus 10-mesh, and marketed in Southern California as roofing granules.  The rest was ground to minus 10-mesh and sold as poultry grit in San Diego.  The property was mostly idle from early 1957 until early 1960, when Weaver began mining limestone from it for use as decorative stone in San Diego region.

      “Photo 49.  View north across limestone milling equipment at Dos Cabezos siding toward Heathman crystalline limestone deposits in low hills in background.  Principal quarry (photo 50) is visible just to left top of wooden loading ramp.”  (pp. 178) “Photo 49. View north across limestone milling equipment at Dos Cabezos siding toward Heathman crystalline limestone deposits in low hills in background. Principal quarry (photo 50) is visible just to left top of wooden loading ramp.” (pp. 178) San Diego Co., CA

      “The Heathman property lies within the area covered by the Dos Cabezas limestone deposits which are shown herein on Fig. 42 and Photo 46.  The property includes a group of low, closely adjacent hills which are underlain by irregularly layered biotite schist, subordinate crystalline limestone, and minor quartzite.  These rocks are cut by irregular intrusive bodies of diorite and quartz diorite and thin dikes of granite pegmatite and aplite.  The layered rocks, which are of preCretaceous age, most commonly strike north-northeastward and dip moderately to steeply west-northwest.  The limestone layers are irregular in plan and vary widely in dip, length and thickness.  Those layers that have been mined range in dip from about 30º -55º northeast, in thickness from 40 to more than 100 feet, and in length from less than 300 to about 1,000 feet.  The limestone is fine- to very coarse-grained, and ranges in color from white, to white with alternating gray bands composed of calcite and finely disseminated graphite, or alternating pale orange bands composed of calcite and finely disseminated garnet.  Uncommonly to sparsely distributed in the limestone are thin layers of schist and thin layers of tactite composed chiefly of red-brown garnet and green diopside.

      “The following average composition was calculated from analyses of four random-type samples collected by O. E. Bowen, Jr. of the Division of Mines and Geology, from the quarry described above:  (analyses by Abbott Hanks, Inc., San Francisco, June 1955):  SiO2, 3.46 percent; Fe3O4, 0.03 percent; Al2O3, 2.46 percent; CaO, 50.68 percent; MgO, 0.96 percent; and P2O5, trace.  In addition to roofing rock, decorative rock, and chicken grit, rocks of this composition might be used as steel flux (if it does not descrepitate when heated) as agricultural limestone, concrete aggregate, ballast, and road base.  Because of the presence of the intrusive rocks, and zones of biotite schist within the limestone layers, these deposits must be mined selectively.

      “The deposit has been worked mainly from two quarries, about 500 feet apart, which are about one-fourth mile north of Dos Cabezas.  The larger of the two quarries is about 125 to 150 feet long, about 50 to 75 feet in maximum width, and 20 to 30 feet high along its main face (Photo 50).  Additional workings comprise three shallow cuts, two of which lie about one-fifth mile northeast of the main quarries, and one which lies about one-fourth mile to the west.  (Also see ‘Unnamed (Lime)’ in the tabulated list.)

      “Photo 50.  Heathman limestone deposit, Dos Cabezes.  Closeup of main quarry shown in center right background of photo 49.  Thin dark layers within limestone are mainly schist.”  (pp. 178) Heathman limestone deposit, Dos Cabezes, San Diego Co., CA

      (pp. 182)

      (Map No.)  296;  (Name of claim, mine, or group)  Heathman (Dos Cabezas, Heathman quarry, Mamie-Heathman) deposit; (Location)  Dos Cabezas area; (Owner name, address)  (blank); (Geology)  (blank).

      (Remarks and references)  “See text.  (Logan 47:302; Tucker 25:370; Tucker and Reed 39:44, pl. 1).”  (To see the bibliography that lists the books cited in the previous sentence, see the “Annotated Bibliographies” section of Geology and Mineral Resources of San Diego County, pp. 283-309.)

  • Dos Cabezas Area, San Diego County, California – the Mamie Heathman Deposit (Limestone)  (from Geology and Mineral Resources of San Diego County, County Report 3, by F. Harold Weber, Jr., Geologist, California Division of Mines and Geology, 1963, pp. 182.  (Used with permission)  (This book is available on the Internet Archive – Texts.)

    (Remarks and references)  “See Heathman deposit in text.”

  • Dos Cabezas, San Diego County, California – the Marie Deposit (Limestone)  (from Geology and Mineral Resources of San Diego County, County Report 3, by F. Harold Weber, Jr., Geologist, California Division of Mines and Geology, 1963, pp. 183.  (Used with permission)  (This book is available on the Internet Archive – Texts.)

    (Remarks and references)  “See Mary Jane deposit.  (Tucker and Reed 39:55, pl. 1).”  (To see the bibliography that lists the books cited in the previous sentence, see the “Annotated Bibliographies” section of Geology and Mineral Resources of San Diego County, pp. 283-309.)

  • Dos Cabezas, San Diego County, California – the Mary Jane (Marie) Deposit (Limestone)  (from Geology and Mineral Resources of San Diego County, County Report 3, by F. Harold Weber, Jr., Geologist, California Division of Mines and Geology, 1963, pp. 183.  (Used with permission)  (This book is available on the Internet Archive – Texts.)

    (Map No.)  300;  (Name of claim, mine, or group)  Mary Jane (Marie) deposit; (Location)  “South edge of the NW ¼ sec. 27, T16S, R8E, SBM; about ½ mile west-northwest of Dos Cabezas siding, on the south side of the San Diego and Arizona Eastern railroad.”; (Owner name, address)  Undetermined (1957); (Geology)  “Two small bodies of crystalline limestone which are about 500 ft. apart.  The more west-northwesterly body consists of a layer of limestone which strikes northeast and dips moderately northwest into the southeast slope of a small hill; the layer is about 250 ft. long and ranges in thickness from 25 to 75 ft.  The more east-southeasterly deposit consists of two low outcrops of siliceous limestone which are surrounded by alluvium.  The larger outcrop is about 200 ft. long and 100 ft. wide.”

    (Remarks and references)  “Developed by shallow cuts.  Output estimated to be less than 500 tons.” 

  • Dos Cabezas (northwest of), San Diego County, California – Unnamed Lime (Limestone)  (from Geology and Mineral Resources of San Diego County, County Report 3, by F. Harold Weber, Jr., Geologist, California Division of Mines and Geology, 1963, pp. 184.  (Used with permission)  (This book is available on the Internet Archive – Texts.)

    (Map No.)  303;  (Name of claim, mine, or group)  “Unnamed (Lime)”; (Location)  About 250 ft. nearly due south of the north quarter corner of sec. 2, T16S, R8E, SBM; about one mile northwest of Dos Cabezas siding.; (Owner name, address)  See “Remarks” column.” (see paragraph below); (Geology)  “Deposit consists of a knob-like exposure of limestone about 250 ft. long, as wide as 50 ft., and as high as 30 or 40 ft.  Limestone is enclosed by metamorphosed diorite and other rocks.  The rock is wavily banded and contains abundant graphite.  Color ranges from medium gray to pale bluish gray or grayish white.  Texture ranges from fine- to medium-grained.”

    (Remarks and references)  “Probably partly within Heathman property (NE ¼ sec. 27) and partly in Anza-Borrego Desert State Park.  Explored by shallow open cuts.  Production negligible.  (Tucker and Reed 39: pl. 1).”  (To see the bibliography that lists the books cited in the previous sentence, see the “Annotated Bibliographies” section of Geology and Mineral Resources of San Diego County, pp. 283-309.)

  • El Cajon (east of), San Diego County, California – the Dehesa Quarry (Granitic Rock) (From The Structural and Industrial Materials of California, Bulletin No. 38, California, State Mining Bureau, San Francisco, California, 1906.)

    "Dehesa Quarry, N. Kessler and Marion Powers, Dehesa, owners. On the north side of the Sweetwater River, a few miles east of El Cajon, is a large mass of gabbro, portions of which are orbicular and are highly ornamental on a polished surface. This rock is mentioned in the XIth Annual Report of the State Mining Bureau, page 95, by H. W. Fairbanks. The orbicular rock was first discovered by Marion Powers, of Dehesa. Prof. A. C. Lawson, of the University of California, gave a short description of it in 'Science' (Vol. XV, p. 415), and a more extended description of it in Bulletin No. 17, Vol. III, Department of Geology, University of California. See also Bulletin 37, 'Gems, Jewelers' Materials, and Ornamental Stones,' State Mining Bureau. W. H. Kessler and W. R. Hamilton, of Stanford University, made a study of this rock and published an excellent illustrated description of it in the American Geologist for September, 1904. The Mining Bureau is indebted to these gentlemen and to the American Geologist for the cuts of the orbicular gabbro shown in this Bulletin.."

    Ill. No. 22.Boulder of Orbicular Gabbro.

    Boulder of Orbicular Gabbro.
    Ill. No. 23.Section of Orbicular Gabbro, Showing General Appearance. White minerals are feldspars. Dark minerals are olivines, hornblendes and hypersthenes. Thickness, about 2 mm. Natural size. Section of Orbicular Gabbro, Showing General Appearance.
    Ill. No. 24. Orbicular Diorite Mine, Dehesa, San Diego County-Near View of Outcrop. Orbicular Diorite Mine, Dehesa, San Diego County-Near View of Outcrop.

    "The gabbro occurs apparently as an intrusive boss in the midst of the granites. It outcrops over an area of about a square mile on the hill at Dehesa, and it is said by Fairbanks to extend 4 or 5 miles southeast. The hill on which it occurs extends about 1200 feet above the river and 1800 feet above sea level. On the slopes in the central portion of the gabbro mass there are scattered boulders of the orbicular rock. The boulders vary in size, some of the larger ones being several feet in diameter. The orbicular rock has not been found in place…."

    "The orbicular gabbro is adapted to interior decoration, because of its variegated texture and coloring. Without being gaudy or bizarre, it has a rich coloring and a unique configuration that will catch and please the eye…."

    "The number and size of the boulders scattered over the surface indicate that there is considerable stone here for commercial purposes, and exploitation may at any time reveal the rock in place. If it should be found in place in sufficient quantities to furnish a constant supply to the market, and to fill any orders in reasonable time, it ought to readily find a place among ornamental stones. It is almost unknown as a commercial product, so that architects would be slow to use it until assured that it is obtainable in quantity.

    "Orbicular gabbro occurs elsewhere in California. There is a specimen in the museum of State Mining Bureau from Rattlesnake Bar, El Dorado County, which was sent in by John Muir, and labeled "Orbicular Diorite (Napoleonite)…."

    "Orbicular granite is said to occur in Rhode Island and in Ontario, but so far as known, no commercial use has been made of it in either place. The same is true of the locality in Davie County, North Carolina."*

    (* Footnote: Orbicular gabbro, diorite from Davie County, N. C., by Thos. L. Watson, Journal of Geol., Vol. XII, p. 294.)

    • El Cajon (east of), San Diego County, California – Dehesa Granite Quarry (Granite) (Excerpt 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 V. "The Counties of San Diego, Imperial," by Frederick J. H. Merrill, Ph.D., Field Assistant (field work in December, 1914), California State Mining Bureau, San Francisco, California, 1916, pp. 427-634.)

      "About 6 miles east of El Cajon on the north bank of the Sweetwater River, and about 1 mile west of Dehesa, in Section 14, T. 16 S., R. 1 E., is a large mass of gabbro, portions of which have an orbicular structure and show a highly ornamental surface when polished.

      "This gabbro is intrusive in the midst of the granite. It outcrops over an area of about a square mile on the hill near Dehesa and extends 3 or 4 miles southeast. The hill on which it occurs rises about 1,800 feet above sea level. On the slopes, in the central portion of the gabbro mass, the orbicular rock occurs in scattered boulders, which vary in size, some of the larger ones being several feet in diameter. It has not, however, been found in place.

      "There are three varieties of this orbicular rock, based on variations in its texture. In the most common variety, an outer ring of feldspar surrounds a nucleus consisting of a crystalline aggregate, much like the ground mass of the rock. Another variety consists of spheroidal bodies showing neither concentric nor radial structure. These appear to be harder and of firmer texture than the surrounding material and, on the disintegration of the rock by weathering, rounded balls remain like pebbles in the residuum. The third variety has both radial and concentric structure.

      "The rock consists of plagioclase, feldspar, anorthite, hornblende, hypersthene and iron oxide. It varies considerably in texture outside of the spheroids, some portions of the mass being rather finely crystalline and others quite coarsely crystalline. Some of the hornblende crystals, in place along joint planes, are several inches in length. The basic character of the orbicular portions is shown by the analysis of an orbule.

      Analysis of an Orbule of the Gabbro by Jas. W. Howson.

      Analysis of an Orbule of the Gabbro by Jas. W. Howson.*

      (Page 675 footnote 1: Univ. of Ca. Dept. of Geol. Bull. No. 17, Vol. III, p. 394.)

      Analysis of the Feldspar of the Gabbro by W. T. Schaller.*

      (* Page 675 footnote 2: Bull. 38, p. 59.)

      "This analysis indicates anorthite or lime feldspar.

      "This orbicular gabbro is adapted to interior decoration, because of its variegated texture and color. Without being gaudy or bizarre, it has a rich coloring and a unique configuration that should catch and please the eye.

      "No definite estimate can be made of the quantity of this stone now available. It is seen only in boulders, and these form but a small per centage of the boulders on the hillside. Their occurrence is such as to leave one in doubt as to whether they came from a single dike-like portion of the mass, or from several separated portions. The number and size of the boulders scattered over the surface indicate that there is considerable stone here available for commercial purposes, and exploration may reveal the rock in place. If it should be found in sufficient quantity to furnish a constant supply to the market, and to fill orders in a reasonable time, it ought to readily find a place among ornamental stones. Since it is almost unknown as a commercial product, architects would be slow to specify it until assured that it is obtainable in quantity.

      "This gabbro area was first mentioned by Fairbanks, R. XI, p. 85. The orbicular rock was first discovered by Marion Powers, of Dehesa. Professor A. C. Lawson, of the University of California, gave a short description of it in Science, Vol. XV, page 415, and a more extended one in Bull. No. 17, Vol. III, Dept. of Geol., Univ. of Cal. W. H. Kessler and W. R. Hamilton, of Stanford University, made a study of this rock and published an excellent illustrated description of it in the American Geologist for September, 1904. See Bull. Nos. 37 and 38, State Mining Bureau.

      "The deposit is controlled by N. Kessler and Marion Powers, of Dehesa."

  • El Capitan Dam (west-northwest of), San Diego County, California – the El Capitan Quarry (Crushed Rock)  (from Geology and Mineral Resources of San Diego County, County Report 3, by F. Harold Weber, Jr., Geologist, California Division of Mines and Geology, 1963, pp. 240.  (Used with permission)  (This book is available on the Internet Archive – Texts.)

    (Map No.)  378;  (Company and Operations – or Deposit)  El Capitan quarry; (Location)  SE. ¼ Sec. 1, T. 15 S., R. 1 E., S.B.M.; about one mile west-northwest of El Capitan dam.; (Status) Inactive since 1935; (History)  Operated 1933-35, during construction of El Capitan dam  (Geology)  Light-gray quartz diorite (Size of Excavation)  Quarry 800-ft. long, 200-300-ft. high  (Products)  Broken stone for use in construction of dam.

    (Mining, Processing, References, and Other Data)  “Probably owned by City of San Diego.”  (To see the bibliography that lists the books cited in the previous sentence, see the “Annotated Bibliographies” section of Geology and Mineral Resources of San Diego County, pp. 283-309.)

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