"Granite is pretty widely distributed over Riverside County. It has been quarried on a large scale for rubble for use in the San Pedro breakwater, at Casa Blanca, and for building and ornamental purposes at Corona, Riverside, and Temecula. At Porphyry and Riverside it has been quarried for broken stone."
Introduction (to Riverside County)
"The.report on the mineral resources of Riverside County is based on field work performed during the summer and early autumn of 1914.
"The examination of the mineral deposits in the desert section of eastern Riverside County, had, on account of the climate, been deferred until autumn, and it was at the inception of this work that, on November 11th, while at Mecca, the writer was stricken by an illness which terminated his field work for the season...well trained and efficient geologist, Mr. Clarence A. Waring, was detailed to complete the unfinished work in eastern Riverside County...."
History (of Riverside County)
"Riverside County, organized by act of the state legislature on March 11, 1893, from portions of San Diego and San Bernardino counties, has an area of 7,240 sq. mil., and a great variety of agricultural and mineral resources. Further, from the diversity of its surface, it affords marked variations in climatic conditions, and, in many areas, offers to the tourist and health seeker, unsurpassed attractions in the several seasons of the year.
Topography (of Riverside County)
"The surface of Riverside County, like that of much of southeastern California, is characterized by bare mountain ranges, separated by nearly level arid belts of varying width. The minor ranges of mountains rise abruptly from the desert plains, having the appearance of being the summits of larger ranges whose bases are buried beneath the loose deposits of the desert. The principal range of Riverside County is that known as the San Bernardino Mountains, the principal summits of which are San Bernardino and San Gorgonio, measuring respectively 10,630 and 11,485 ft. in altitude. The range is flanked on the southwest by the broad valley and plain of western San Bernardino County which terminates to the southeast in the narrow valley known as the San Gorgonio Pass, the summit level of which at Beaumont, measures 2570 ft. South of San Goronio Pass is the lofty range of southeast trend known as San Jacinto, and its lofty peaks, San Jacinto and Tahquitz, measuring respectively 10,805 and 8825 ft. in altitude. To the eastward the slopes of the San Jacinto Range decline rapidly toward the plain known as Coachella Valley and desert, Coachella being the corruption of the old Spanish name Conchilla. To the southeast, the Coachella Valley terminates in the Salton Sink, which has been carefully mapped by the U. S. Geological Survey and has been discussed in our report on Imperial County.
"Central Riverside County is marked by several small desert plains. One of these, south of Riverside and west of Perris, is a striking topographic feature. This and others are clearly shown on the U. S. G. S. topographic map known as Southern California Sheet No. 1, to which the reader is referred for further detail.
Geology (of Riverside County)
"The geology of Riverside County has not yet been studied in detail. The first careful reconnaissance made through this region was in the latter part of the year 1853, when Professor William P. Blake, as geologist of the expedition under Lieutenant R. S. Williamson to determine a route for a transcontinental railroad, traversed the San Gorgonio Pass toward the Coachella Valley and the Salton Sink...."
Mineral Resources (in Riverside County)
"The mineral resources of Riverside County are varied and of material importance, having amounted in 1914 to $1,579,586.* But it has never been a large producer of metals, and, as the figures show, its chief mineral wealth lies in nonmetallic products...."
(* Page 524 footnote: See C. S. M. B., Bull. No. 70, pp. 98-99.)
Nonmetals (in Riverside County)
"Under this head are included the more valuable of this county's mineral products. Clay alone aggregated in 1914 a total of nearly $70,000 and the other nonmetallic minerals amount in value to a very substantial sum.
"The principal materials under this head are Clay, Gypsum, Cement, Stone, Magnesite, and Gems."
Cement (in Riverside County)*
"Cement, as used in building, is a compound of lime, alumina, and silica that hardens in contact with water. It differs from quicklime in that it does not slake, expand, crumble, nor give off heat when wet, but chemically combines with part of the water into a firm, artificial stone. There are two principal classes of cements: the natural rock, or Rosendale cement; and the artificial product or Portland cement, to which may be added a third, the Pozzuolana or slag cement...."
(Page 553 footnote: Bull. 38, pp. 171-173.)
Building Stone (in Riverside County)
"That there is a great wealth of valuable stone in California has been known for years. It is equally well known that much of it is undeveloped, a considerable portion of the building and ornamental stone used in this state being imported from other states and from Europe (circa 1915).
Uses of Stone (in Riverside County)
"Stone is used in substructures very extensively. Wood, concrete, brick, and iron are frequently used as a substitute in superstructures, but where first cost can be subordinated to architectural effect, stone will, in most cases, be used.
"For funeral monuments there is no satisfactory substitute for stone, and for this purpose it is often shipped long distances, in order to get one that has an established reputation. Many of the monuments in this state are of stone from New England, Indiana, Georgia, or Europe, and often a large part of the cost of the monument is in railroad and water freight.
"Some other uses of stone are in the construction of breakwaters, bridge abutments, culverts, curbing, fences, flagstones, hitching posts, macadamizing, paving blocks, piers, retaining walls, reservoirs, sewers, sluiceways, etc.
Granite (in Riverside County)
"This stone is widely distributed over Riverside County. It has been quarried on a large scale at Casa Blanca for rubble used in the San Pedro breakwater, and for building and ornamental purposes at Corona, Riverside, and Temecula. At Porphyry and Riverside has been quarried for broken stone. The Casa Blanca quarries have long been idle.
"Besides its use for paving, the Corona granite is used to some extent for building stone, and in considerable quantities for monuments in Los Angeles, Riverside and other places in southern California.
"The monument dealers in southern California nearly all speak highly of Corona granite for monuments, thus giving it a reputation in that field. Its nearness to Los Angeles and Riverside also favors the use of this stone for 'Belgian' (paving) blocks.
"The stone from all the quarries is hauled by wagon to the railroad at Hammer switch, about a mile east of Porphyry station."
Population: 60,297 (1920 census)
Location: Southern portion of state.
"Riverside is the fourth county in the state in size and the thirteenth in regard to the total value of mineral output for 1919. Within its borders are included mountain, desert, and agricultural land. Its mineral resources include metals, structural and industrial materials, and salines, some of the more important being borax, brick, cement, clay, coal, copper, feldspar, gems, gold, gypsum, iron, lead, limestone, manganese, magnesite, marble, mineral paint, mineral water, salt, glass-sand, soapstone, silver, miscellaneous stone, and tin. In point of variety Riverside County led all others with nineteen different minerals commercially produced in 1919, passing San Bernardino which dropped from twenty-five to seventeen.
"The increase in 1919 over the 1918 value of $1,689,042 is due mainly to cement.
"Commercial production for 1919 was as follows:
(Headings for the information below are: Substance, Amount, and Value.)
Brick and tile, ---, $224,379
Clay, 42,207 tons, $61,006
Copper, 10,590 lbs., $1,970
Gold, ---, $400 (estimated)
Granite, ---, $17,975
Gypsum, 200 tons, $425
Manganese, 1,808 tons, $49,324
Silica, 3,034 tons, $15,112
Silver, ---, $102,399
Stone, miscellaneous, ---, $102,399
Other minerals,* ---, $2,103,760
(Total value) $2,578,250
(* Includes cement, coal, feldspar, fuller's earth, lead, magnesite, mineral water and potash.)
"About two-thirds of the area of Riverside is in the arid Colorado Desert where there are numerous large outcrops of pre-Cambrian and pre-cretaceous rocks. These probably contain some large deposits of limestone, but the region lacks the railroad facilities enjoyed by San Bernardino County, and the deposits are so remote from transportation that they have received little attention.
"The principal production has come from the deposits at Crestmore in the western part of the county and from smaller deposits as far east as Whitewater and Palm Springs, as well as in the region of Hemet and San Jacinto, where railroad service is available. In general, these deposits are Paleozoic or older (but analyses of the limestone suggest Carboniferous), and have been intruded by or are enfolded in Jurassic granitic rocks.
"The Crestmore limestone deposits have been widely known and studied for many years by mineralogists because of the great variety of minerals occurring there in the contact zones between the limestone and the intrusive rocks. The late Professor Arthur S. Eakle called attention to this rich mineral field and described some of the rare minerals in 1914. In a late article, A. O. Woodford (43)* has listed and described 112 named minerals and 14 unnamed from these deposits. His paper is also of interest for its detailed study of the geology of the deposits.
(* A. O. Woodford, "Crestmore Minerals," California Division of Mines Report 39, pp. 333-365, 7 figs, 1943.)
"Aside from the quarrying of limestone for making cement at Crestmore, there has been only one other producer of limestone in the county for several years, and he reported no output in 1946."