"In shape this county is nearly a rectangle, with the longer axis northwest and southeast. It is bounded on the east by Riverside County, north by San Bernardino and Los Angeles County when the latter was organized in February, 1850, but in March, 1889, Orange was separated into a distinct county. It has a shore line of about 40 miles.
"About three-fifths of the area of this county is valley land and the remaining two-fifths is mountain and foothill land. The Santa Ana range of mountains is the line between Orange and San Bernardino counties at the northeast corner of the former county. It is also the dividing line between Orange and Riverside counties on the east. This range also sends up a line of foothills westwardly along the seashore nearly half way across the county. The highest point is locally known as Saddleback, or Santa Ana Peak. In an early day this was known as Santiago Peak, but in 1861 it was ascended by Prof. J. D. Whitney, then State Geologist, who named it Mt. Downey, in honor of J. G. Downey, Governor of California. He found the elevation to be 5,675 ft. above the sea level. All of the western portion of the county is included in the Santa Ana plain or valley. There are also several small valleys among the foothills and along the mountain streams. The Santa Ana plain is covered with a rich loam, and, with the exception of some patches of alkali, is very productive.
Mineral Resources (in Orange County)
"Orange County stood second in the list of mineral producing counties of California for the year 1914; due mainly to petroleum. Other items yielding in commercial quantities are: clay products, natural gas, and miscellaneous stone.."
"Some years ago tests in the manufacture of cement were made by using clay and the fossiliferous limestone found on the ranch of William L. Moulton, near El Toro. The product was of satisfactory quality, but the high cost of fuel at that time prevented the manufacture from a commercial standpoint. With the present supply of oil as fuel, cement could probably be produced commercially from the limestone and clay found on this property."
Stone Industry (in Orange County)
"Crushed rock, sand and gravel were reported by the county assessor as produced in considerable quantities in Orange County during 1914. The materials were used for concrete and road work."
Area: 795 square miles
Population: 61,375 (1920 census)
Location: South-western portion of state, bordering Pacific Ocean
"Orange County is one of the many in California which on casual inspection appears to be anything but a mineral-producing section. It stands, however, as the second county in the state in regard to the total value of mineral output for 1919, its highly productive oil fields making such a condition possible.
"This county, in company with most of the other oil counties, shows a gain in 1919, with a total value of mineral products of $27,848,727 from the 1918 output, worth $22,914,660. It passed Shasta County in 1917, which previously for a number of years, had exceeded all other counties in California, except Kern.
"Aside from the substances actually produced and noted in the table below, coal, gypsum, iron, infusorial earth, sandstone, and tourmaline have been found in Orange County.
"Commercial production for 1919 was as follows:
(Headings for the information below are: Substance, Amount, and Value.)
Clay and clay products, ---, $18,489
Natural gas, 12,039,355 M. cu. ft., $837,439
Petroleum, 14,458,722 bbls., $26,893,223
Stone, miscellaneous, ---, $1,944
Other minerals*, ---, $97,632
(Total value) $27,848,727
(* Includes lead and potash.)
"Orange County is covered mostly by geologically young sedimentary formations, with some older rocks in the eastern part. There has been little production of limestone, and none has been recorded in recent years. In the eighties, when the erection of portland cement plants was first being urged in this state, two of the soft limestone deposits in this county were mentioned as possible sources of material. These were on Rancho Canada de Los Alisos, and near San Juan Capistrano."
(* Please note this list does not include sand or gravel quarries.)
"Capistrano. Sec. 31, T. 7 S., R. 7 W., S. B. M.; R. Egan, Capistrano, owner. A deposit of fossiliferous limestone, used by the padres to burn lime for the mission buildings."
"Capistrano. Sec. 31, T. 7 S., R. 7 W., S. B. M., R. Egan, Capistrano, owner. A deposit of fossiliferous limestone, used by the padres to burn lime for the mission buildings."
"Capistrano deposit is in sec. 31, T. 7 S., R. 7 W., S. B., 1 mile northeast of San Juan Capistrano. It is said to have been used by the padres in building the San Juan Capistrano Mission. It is in an area mapped as upper Miocene."
"A new cement has been discovered in Orange county, California, that gives promise of great wealth. It is located near El Toro."
"William Moulton. Extensive beds of this fossiliferous limestone are found on Moulton's ranch, south of El Toro. (See Cement.) The following analysis of this limestone is reported: carbonate of lime, 96 per cent; silica, 2.5 per cent; alumina, 1 per cent; iron oxide, 0.5 per cent."
“Some years ago tests in the manufacture of cement were made by using clay and the fossiliferous limestone found on the ranch of William L. Moulton, near El Toro . The product was of satisfactory quality, but the high cost of fuel at that time prevented the manufacture from a commercial standpoint. With the present supply of oil as fuel, cement could probably be produced commercially with the limestone and clay found on this property.”
"El Toro. A similar limestone was burned about 1888, but the kiln was abandoned after a campaign not lasting two years. Extensive beds of this fossiliferous limestone are found on Moulton's Ranch, south of El Toro...."
"El Toro deposit is on the old William L. Moulton Ranch 3 ½ miles south of El Toro. A crushing plant was operated on the deposit in 1923 (Tucker 25b, p. 68)* and crushed limestone was sold locally as a soil corrective and fertilizer, but there has not been any recorded production since. The deposit is of good size and is soft fossiliferous limestone in an area shown on the state geologic map as upper Miocene. Forty years ago it was tested for making portland cement with clay found nearby, and was said to be satisfactory. At that time an analysis was reported to show 96 percent CaCO3, 2 ½ percent SiO2, 1 percent Al2O3 and 0.5 percent Fe2O3. It is believed that the average run of the deposit would show less CaCO3 and more of the other ingredients as these soft limestones along the coast generally carry some clay."
(* W. Burling Tucker, Los Angeles Field Division, "Orange County," California Mining Bureau Report 21, pp. 58-71, illus., 1925.)
El Toro Station, Orange County, California - Lime Kiln - Excerpt from the Tenth Annual Report of The State Mineralogist For The Year Ending December 1, 1890, California State Mining Bureau, Sacramento: State Printing Office, 1890.
General Geology. (pp. 399-400)
“The Santa Ana Range proper belongs to the Cretaceous age. The Sango Creek and Cañon seem to divide the cretaceous from the Tertiary,...least the foothills on the west side contain Miocene fossils. While the eastern side of the cañon furnishes several beds of fossils, I was...able to find any immediately on the western side until El Toro was..., several miles distant. At this place is a most remarkable bed of fossils. It is about ten miles from the ocean and nearly one and half miles southwest of El Toro Station. An exposure has occurred excavating into the bed of fossil shells in view of burning for lime, the exposure the stratum is about seven feet thick, dipping to the south and can be traced for nearly half a mile....”
Orange County, by Dr. Stephen Bowers, Assistant in the Field, pp. 406.
“El Toro Station is at a bend of Alisos Cañon, nine miles from the ocean. A plain here debouches into the Santa Ana Valley. Not far from the station is a lime kiln, where lime is manufactured from fossil shells, to which I have previously referred in this report. The elevation of El Toro is nearly six hundred feet....”
"El Toro. A similar limestone was burned about 1888, but the kiln was abandoned after a campaign not lasting two years."
"Ladd Canyon deposit is in secs. 3 and 4, T. 5 S., R. 7 W., and sec. 33, T. 4 S., R. 7 W., S.B. It is about 15 miles by road east of Orange to the mining camp of Silverado. From near there, an old dirt road runs 3 to 4 miles along Ladd Canyon to the above sections where 10 mining claims were located over 20 years ago. The limestone in this region was investigated by Harold W. Fairbanks (93a, pp. 115, 116)* in 1891-1892 and he reported gathering from it fossil specimens which were pronounced Carboniferous in age by the National Museum. The limestone is gray to black, not crystalline, occurs in bunches, the largest reported by Fairbanks being 100 feet thick; others claim thicker deposits. The deposits extend toward the summit of the Santa Ana Mountains at elevations of 2200 to 2900 feet.
(* Harold Wellman Fairbanks, "Geology of San Diego County, also of Portions of Orange and San Bernardino Counties," California Mining Bureau Report 11, pp. 76-120, illus. 1893.)
"The following analysis of the limestone was made by F. W. Huber, University of California, over 20 years ago.
SiO2, 1.34 percent
CSaO, 51.45 percent
Fe2O3 and Al2O3, 1.95 percent
MgO, 1.86 percent
Ignition loss (CO2 and H2O), 43.08 percent
Undetermined, 0.32 percent
"So far is known, the deposits are undeveloped."
Mission San Juan Capistrano Quarry - See: Capistrano, Orange County, California - Limestone Deposit (Limestone)
"Santiago Sandstone Quarry, in Sec. 17, T. 5 S., R. 7 W., S. B. M.; Rev. C. Gruen, 814 Rose street, Santa Ana, owner. This side canon runs along a fault, dividing the sandstone from the shale.
"The sandstone is quite hard, of a light gray color, rather coarse-grained, with inclusions of igneous material rounded and waterworn. The large blocks are broken down with powder, hand-drilling, and are split to the required dimensions by driving a few wedges. the stone is used for building purposes in Santa Ana."