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California Stone Industry (historical account up to 1966)

Excerpts From

Mineral Resources of California, Bulletin 191,
California Division of Mines and Geology, San Francisco, California, 1966.

(Please note: Use the drop down box below to jump to the individual sections of this document.)

Stone, Crushed and Broken, by H. B. Goldman, California Division of Mines and Geology, San Francisco, Calif. (circa 1966)

"Stone production is one of the oldest and most extensive mineral industries in California. In the late 1800's, dimension stone was produced in the State in much greater volume than crushed stone. During the past 50 years the output of dimension stone has dwindled, while the production of crushed stone has increased many fold. Greatly increased use of crushed stone for aggregate, especially in asphalt concrete for paving, the marked decrease in use of dimension stone for building stone, paving blocks, or curbing is largely responsible for this trend.

"In 1964, California ranked third among the states in stone production, with a total output of approximately 45,710,000 short tons, valued at $61,391,000. Crushed stone ranked in value only behind petroleum products, cement, and sand and gravel, among California's mineral commodities.

"Although the terms 'rock' and 'stone' commonly are used synonymously, they have different meanings when strictly applied. 'Rock' has been defined variously by geologists, but in the stone industry it is applied to any mass of mineral aggregate as it exists in its natural state and in place. 'Stone' refers to individual blocks, asses, or fragments that have been broken or quarried from bedrock exposures, and are intended for commercial use.

"Most deposits of economic minerals have formed under relatively uncommon geologic conditions, but stone is obtained from the ordinary rocks that constitute the earth's crust. The materials that can be classed as stone are numerous, widespread, and a wide range of geologic ages and modes of origin.

"Stone has many industrial applications, but these can be divided into two classifications by usage: (1) crushed and broken stone, and (2) dimension stone. Crushed and broken stone includes all stone in which the shape is not specified, such as that used as aggregate, railroad ballast, and riprap. Dimension stone is produced to specified dimensions, and includes stone employed as building stone, monumental stone, curbing, and flagstone (see section on Dimension stone in this volume) (On our web site, the section on dimension stone, follows this section.)

"For most uses, crushed or broken stone should be durable, dense, sound, hard, strong, able to withstand high temperatures, and tend to break into suitably shaped fragments. In almost all uses, stone must resist the chemical action of weathering. Stone to be used for certain special purposes, such as the limestone used in agriculture, glass manufacture, or the sugar refining industry, must be chemically suited to these applications.

"Crushed and broken stone commonly is further subdivided, on the basis of use, into (1) crushed stone, (2) riprap, (3) furnace flux, (4) refractory stone, (5) agricultural stone, and (6) stone used for other purposes. Crushed stone is mainly used as aggregate in asphalt concrete for paving purposes, railroad ballast, aggregate base, and concrete for paving purposes, railroad ballast, aggregate base, and fill. Riprap consists of large broken stone used without a binder, principally for jetties, breakwaters, and seawalls which are intended primarily to resist the physical action of water. Furnace flux consists of limestone and marble used for chemical purposes in the refining of iron ores and in other metallurgical practices. Refractory stone, such as quartzite, mica schist, dolomite, and soapstone is used in the manufacture of refractory brick, and for furnace and ladle linings. Agricultural stone includes any type of stone that is added to soil, either as a fertilizer or a soil-conditioner. The category 'other purposes,' includes crushed stone used as a filler, poultry grit, roofing granules, stone, sand, and terrazzo granules; in the production of mineral wool, stucco, artificial stone, and mineral food; in coal mine dusting; and for various chemical applications.

"Many materials, that by definition can be classified as stone are considered as separate commodities. Dolomite, limestone, vein quartz and quartzite, sand and gravel, and specialty sands, as well as such stone-like nonmetallic materials as diatomite, pumice, perlite, volcanic cinders, and soapstone are described more completely elsewhere in this volume.

Rocks used as crushed and broken stone in California

"The stone industry recognizes the following stone classification based mainly on composition and texture: (1) granite; (2) basalt and related rocks; (3) limestone; (4) marble; (5) sandstone; and (6) miscellaneous stone (including conglomerate, greenstone, shale, mica schist, and tuffaceous volcanic rocks). Most of these types are abundant and widespread in California, as shown on Figure 76, and listed in table 46.

Table 46. Principal crushed and broken stone in California
(circa 1966)

[Locations shown on fig. 76]


1. Union Granite Co., Rocklin, Placer County.
2. Guy F. Atkinson, Riverside, Riverside County.
3. J. B. Stringfellow, Riverside, Riverside County.
4. Granite Rock Co., Watsonville, San Benito County.
5. Hansen, Silvey, and Sinnott, Felton, Santa Cruz County.


6. Blake Bros., Richmond, Contra Costa County.
7. Quarry Products, Inc., Point Richmond, Contra Costa County.
8. Sweetser Bros., Rosamond, Kern County.
9. Basalt Rock Co., McNear Point, Marin County.
10. Hutchinson Co., Greenbrae, Marin County.
11. Pacific Cement and Aggregate, Inc., Brisbane, San Mateo County.
12. Guy F. Atkinson, Rincon, Santa Barbara County.
13. Rancho Guadalasca, Camarillo, Ventura County.

Basalt (and Related Volcanic Rocks)

14. Gallagher and Burk, Inc., Oakland, Alameda County.
15. A. C. Goerig, Orinda, Contra Costa County.
16. Basalt Rock Co., Inc., Novato, Marin County.
17. Basalt Rock Co., Inc., Napa, Napa County.
18. Don Weaver, Jucumba, San Diego County.
19. J. M. Nelson, Cordelia, Solano County.
20. Hein Bros. Basalt Rock Co., Petaluma, Sonoma County.


21. California Rock and Gravel Co., Cool, El Dorado County.
22. San Leandro Rock Co., San Leandro, Alameda County.
33. Ryolite Corp. of California, Altaville, Calaveras County.
34. Henry J. Kaiser, Clayton, Contra Costa County.
35. Pacific Cement and Aggregates, Clayton, Contra Costa County.
36. Gravelle and Gravelle, Trinidad Quarry, Humboldt County.
37. Desert Rock Milling Co., Randsburg, Kern County.
38. Connolly-Pacific Co., Catalina Island, Los Angeles County.
40. Minnesota Mining and Mfg. Co., Corona, Riverside County.
41. Brubaker-Mann Co., Barstow, San Bernardino County.
42. Canyon Rock Co., San Diego, San Diego County.
43. Kenneth H. Golden Co., San Diego, San Diego County.
44. Robert Guerra, Morrow Bay, San Luis Obispo County.
45. Mirassou Bros., Los Gatos, Santa Clara County.


46. Placerville Slate Products, Placerville, El Dorado County.

Figure 76. Principal crushed and broken stone quarries in California; numbers refer to table 46.

Principal crushed and broken stone quarries in California

Granite (in California)

"The term 'granite' is commonly applied to medium- to coarse-grained igneous rocks that consist mainly of feldspar and quartz, with subordinate amounts of ferromagnesian minerals. In the stone industry, and in the following discussion, the terms 'granite' and 'granitic rock' are used even more broadly to refer to various intrusive igneous rocks with gneissic textures.

"Most unweathered granite rocks are hard, strong, tough, and resistant to abrasion, impact, and chemical attack. These properties make granitic rock well suited to use as building stone, riprap, and aggregate.

"Granitic rocks occur mainly in large bodies, known as batholiths, which are exposed over many square miles. In California, granitic rocks occur mostly in the Sierra Nevada and southern California batholiths and in smaller masses in the Klamath Mountains and the desert regions of eastern and southern California. These bodies together underlie about 40 percent of the State's area and are largely or wholly of Mesozoic age. Batholiths commonly consist of numerous individual bodies of various granitic rock types, with contrasting colors, textures, and mineral composition. The two great batholiths of California are exposed mostly in mountainous areas, but the main granite quarries lie about their peripheries or in outlying smaller masses, so that the quarries are as close as possible to major transportation routes to centers of consumption. Over wide areas of the State, the exposed granitic rocks are so deeply weathered or highly fractured as to be unsuited to the purposes outlined above. In the Los Angeles area for example, little or none of the granitic rock exposed in the nearby Santa Monica or San Gabriel Mountains is sufficiently unshattered or unweathered to be quarried as crushed stone in large tonnages, and all granitic stone must be brought to the Los Angeles area from quarries in Riverside, San Diego, and San Bernardino Counties, 45 to 100 miles away. Disintegrated and shattered granitic rock, known commercially as decomposed granite, or 'DG' is much used in southern California as aggregate base, low-quality paving material, and fill.

"In California, granitic rock, has been quarried mainly for use as dimension stone and riprap, but the quarry waste has been a source of crushed stone for local use.

"The following granite quarries were active in 1964: near Rocklin, Placer County; Logan, San Benito County; the Jurupa Mountains and vicinity, Riverside and San Bernardino Counties; and near El Cajon, San Diego County.

Decomposed Granite (in California)

"Weathering may decompose the feldspar and ferromagnesium minerals in granitic rock, and convert once-sound rock in situ to a weak, relatively friable mass of quartz grains, clay, and partially decomposed grains of feldspar and ferromagnesian minerals. Granite that has been shattered by fault action is particularly susceptible to decomposition by weathering. Weathering in sedimentary deposits of granitic debris may render the stone unsound for use as aggregate and if sufficiently advanced, convert the deposit to the equivalent of decomposed granite.

"As an extremely low-cost material employed in relatively non-exacting uses, decomposed granite can rarely be economically hauled farther than a few miles to the site of use. Therefore, it is used extensively only in those sections of California where it occurs near metropolitan areas, especially the Los Angeles and San Diego areas.

Basalt and Related Rocks (in California)

"In commercial usage, and in this discussion, the term 'basalt' is applied to any of the dense, fine-grained, dark-gray or black volcanic rocks. The term ordinarily includes rock types that geologists classify as dacite, andesite, basalt, trachyte, or latite.

"Basaltic rocks are characteristically hard, tough, and durable, so are best suited for use as aggregate, railroad ballast, and riprap. Some types of crushed basaltic rock are well suited for use as artificially colored roofing granules.

"Basaltic rocks are extensively exposed in many localities in California. In the northeastern part of the State, Tertiary and Quaternary basaltic rocks are exposed for hundreds of square miles in the Modoc Plateau and form the most extensive occurrences. A number of smaller areas, measurable in tens of square miles or less, occur scattered in the Sierra Nevada and Mojave Desert provinces in the northeastern portion of central and southern California. Little basaltic stone is obtained from these areas because of their remoteness from the main centers of use, but some has been quarried for local construction projects and for railroad ballast.

"Less extensive occurrences in the Coast and Peninsular Ranges are the sources of most of the basaltic stone produced in the State. Notable quantities of basaltic stone are produced near Napa, Marin County; Novato, Marin County; Orinda, Contra Costa County; Cordelia, Solano County; and Jucumba, San Diego County.

Limestone and Marble (in California)

"Carbonate rocks are abundant and commercially important in California (see section on Limestone, dolomite, and lime products, including cement.)

"In the stone industry the term limestone is applied to many types of rock that contain a high percentage of calcium carbonate, although large proportions of other substances also may be present. They also commonly contain clay, silt, and sand grains. A high percentage of clay commonly weakens carbonate rock, and makes it unfit for use as stone; a high content of sand grains or silica may make carbonate rock too hard to be prepared for use economically.

"The term 'marble' is applied to any carbonate rock that will take a high polish and includes various dense types of limestone and dolomite. The term is also loosely applied to coarsely crystalline carbonate rocks. The classification of carbonate rock either as limestone or marble therefore is determined largely by its use. Stone for many California deposits, for example, has been used both as limestone (e.g., in the sugar industry) and as marble. Nearly all of the crushed carbonate stone produced in California is classified as limestone.

"For use as stone, carbonate rock should be physically sound, dense, and relatively pure. Carbonate stone that is strong, tough, and durable is well suited for use as concrete aggregate, road metal, railroad ballast, and rip rap. A pure-white color also is desirable in carbonate stone to be used for granules in built-up roofing, and various colors are desirable in granules to be used for terrazzo.

"Most of the carbonate stone produced in California in recent years has been used primarily for its chemical properties, and has been consumed in the cement, lime, agricultural, and various other process industries. Relatively smaller tonnages have been produced for use as crushed and broken stone primarily as by-products of cement company operations.

"Occurrences of carbonate rocks are extensive and widespread in California. Deposits are especially numerous in the western Sierra Nevada Province, the northeastern portion of the Klamath Mountains province, the Great Basin, and Mojave Desert provinces in southeastern California; in the Coast Ranges, mainly south of San Francisco, and in the Peninsular and Transverse Range provinces of southern California. The ages of these deposits range from Precambrian to Miocene.

Sandstone (in California)

"Sandstone is a clastic sedimentary rock composed of particles mainly in the size range of about one-fourth to one-hundredth of an inch in diameter. Some sandstones consists almost wholly of quartz grains, but most sandstones are feldspathic and some contain a high proportion of ferromagnesian minerals. The strength and durability of sandstone are mainly determined by the type of material that cements the grains together. Only well-indurated sandstone, cemented with silica or calcite (rather than with the weaker cements, clay or iron oxide), is suited for use as crushed and broken stone.

"Most of the sandstone that occurs in California is very friable, but some is sufficiently durable to be used for riprap, railroad ballast, portland cement, concrete aggregate, and bituminous aggregate.

"Virtually all the sandstone in California occurs in formations that lie within the age range of Jurassic to Quaternary. Commonly the older sandstones are harder and stronger than the younger ones, hence are better suited to be used as crushed and broken stone.

"Sandstone is extensively exposed in most of the western and central parts of the State, but sandstone for use as crushed and broken stone has been produced mainly in the San Francisco Bay area at quarries in Marin and Contra Costa Counties.

Miscellaneous Stone (in California)

"In addition to the four main categories described previously, many varieties of rock types have been quarried throughout California and are grouped under the heading of 'Miscellaneous stone'. Significant production is obtained from conglomerate, greenstone, slate, tuff, and metavolcanic rocks.

"Rocks classifiable as greenstone in this broader sense are moderately abundant in many parts of California, but relatively small tonnages are used as crushed and broken stone. Many occurrences of greenstone are outside the range of economic haulage to main centers of use, and much of the more readily available greenstone is of inferior quality.

"Much of the crushed greenstone is employed for uses in which a green color is specifically desired, such as for naturally colored roofing granules. Physically sound greenstone also may be used for aggregate, ballast, riprap, or fill, if it is available economically.

"Some of the most extensive occurrences of greenstone in California are in the Franciscan Formation, in the northern and central Coast Ranges, and in the upper Palezoic (sic) Calaveras Formation and the Jurassic Amador Group along the west flank of the Sierra Nevada. Much of the green pyroclastic sedimentary rock quarried in Kern County since World War II for roofing granules could be classed as greenstone.

"Slate is a thinly foliated metamorphic rock composed essentially of muscovite (sericite), quartz, and graphite, all in grains of microscopic or submicroscopic size. Slate is formed by compaction and partial recrystallization of shale, is commonly dark colored and moderately hard.

"Slate is desired mainly for use as dimension stone (see section on Dimension stone). Its chemical inertness, resistance to weathering, and flat particle shape make crushed slate a desirable material for roofing granules and filler dust.

"Extensive exposures of slate of the Jurassic Mariposa Formation occur along the western flank of the Sierra Nevada. Minor bodies of slate, mostly of low quality, occur in pre-Tertiary metamorphic rocks at several scattered localities in the State.

"The state's principal source of crushed and pulverized slate is the Chili Bar mine, El Dorado County, which has been active since 1962. Here the slate is mined in extensive underground workings and is used for roofing granules and filler dust.

"The term 'tuff' embraces pyroclastic volcanic rocks, most of which would be classed as rhyolite or dacite tuffs or tuffaceous sediments. Most tuffaceous rocks are only moderately hard, although on exposure to air they commonly harden appreciably. As many tuffs are attractively colored and workable, they have been extensively used for building stone (see section on Dimension stone). Because of its softness, tuffaceous rock is unsuited to most uses of crushed and broken stone but it is extensively used in the production of colored roofing granules.

"Dark dense Metavolcanic rocks are excellent sources of riprap, crushed stone and roofing granules. Quarries are active in San Diego, San Diego County; Corona, Riverside County; and Clayton, Contra Costa County."

Stone, Dimension, by H. B. Goldman, California Division of Mines and Geology, San Francisco, Calif. (circa 1966)

"Dimension stone production is among the oldest and largest of the mineral industries of California; commercial quarries were operated as early as 1854 at Monterey and Point Reyes. Until the early 1900's the production of dimension stone, mainly for use in buildings, paving, and curbing, greatly exceeded that of crushed stone, but since then, the dimension stone output has dwindled while production of crushed stone has increased many fold. The development of steel-frame buildings, which require comparatively little stone, and the introduction of concrete, which is much less expensive and more conveniently used than stone, combined to cause this decline.

"The term 'dimension stone' is applied to natural stone that is cut to definite size and shape and includes cut, carved, and roughhewn blocks of building stone, paving blocks, curbing, flagging, and cut and polished monumental stone.

"The recorded production of dimension stone in California from 1887 to 1964, totals approximately 58 million dollars, as shown in dollars was produced in the State. This stone was used principally for monumental and building stone. Rock types quarried in 1964 were granite, light-colored volcanics, siliceous limy shales, mica schist, slate, and quartzite.

"Dimension stone is subdivided by uses into building stone, monumental stone, paving stone, curbing, and flagging. One of the principal uses of dimension stone is as a construction material. Included in this category is stone in any form that constitutes a part of a structure. Whereas building stone formerly was a basic construction material, its present function is largely ornamental. Building stone is marketed as rubble, rough building stone, ashlar, and cut or finished stone.

Specifications of Rock Used for Dimension Stone

"Only a small portion of the rock that comprises the earth's crust can satisfy the exacting specifications for most dimension stone. Freedom from cracks and lines of weakness is essential. Uniform texture and grain size together with an attractive color are generally required. The rock must be free from such minerals as pyrite, marcasite, and siderite, which oxidize upon weathering to cause deterioration or surface staining. A rock that splits easily in 1 or 2 planes is desirable. Many rocks, particularly granites and sandstones, split in some directions with greater ease than in others.

Figure 77. California dimension stone production, 1887-1963.

\Figure 77. California dimension stone production, 1887-1963

Rock Used as Dimension Stone in California

Granite and Related Rocks

Granite, defined geologically, is a medium- to coarse-grained crystalline rock that consists essentially of potassium feldspar, subordinate, sodic feldspar, and quartz. In the stone industry the term 'granite' is used more broadly to refer to various intrusive igneous rocks with granite textures, and even some metamorphic rocks with gneissic textures. Such igneous rocks as syenite, granite, granodiorite, quartz monzonite, diorite, and gabbro, which range in color from light to dark and in composition from acidic to basic, commonly are referred to commercially as 'granites.'

"Granite has comprised approximately 75 percent of the total dimension stone produced in California. In 1963, dimension stone granite valued at $1,564,271 was produced in the State. Principal sources of this and other dimension stone types are shown on figure 78.

Figure 78. Principal sources of dimension stone in California.

Principal sources of dimension stone in California


"Granitic rock underlies about 40 percent of California's land area and occurs mostly in the large bodies known as the Sierra Nevada and Southern California batholiths, and in smaller bodies exposed in the Klamath Mountains and in the desert regions of the State.

Quarries in the Sierra Nevada batholith. Quarries in the Sierra Nevada batholith have yielded approximately half of the granite dimension stone, and about 40 percent of all the dimension stone produced in California. The most productive districts have been at Raymond, Madera County; Rocklin, Placer County; and Academy, Fresno County. Smaller areas were active at Folsom, Sacramento County; Porterville, Tulare County; Nevada City, Nevada County; and Susanville, Lassen County. The quarries have been located mainly on low rounded outcrops in the foothill area where the granite was exposed at the surface, or as residual boulders. The periods of greatest activity were 1889-1895, 1903-1905, and 1920-1930.

"The principal source of granite in California has been the Raymond district in Madera County. This district which was active mainly from 1888 to about 1943, has a total production valued at about 10 million dollars. Granite is quarried from a broad exfoliated dome about 700 feet in diameter. The oldest and most productive of the quarries, that of the Raymond Granite Co., was acquired in 1953 by the Cold Spring Granite Co. of Minnesota and was still active in 1965.

"Granite similar to that quarried at Raymond has been quarried in Placer County from an area that extends from Rocklin to Newcastle. Since 1863, granite valued at well over 3 million dollars has been produced for this district. Quarrying has been confined to the gently rolling plain, approximately 5 miles long and 1 to 2 miles wide, that extends from Rocklin to Penryn. In 1965, the Union Granite Co. operated a quarry near Loomis.

"Granite dimension stone valued at more than $650,000 has been produced in the Sierran foothills 1 mile northeast of Academy in Fresno County. In this district a dark-colored augite gabbro-diorite crops out as residual surface builders and as massive ledges underlying low rounded hills. Nine quarries in all have been worked in a 100-acre area. In 1964 the Raymond Granite Co. operated a quarry in this area.

"Granite valued at $740,000 has been produced in Tulare County from three quarries in the foothills east of Porterville and Exeter.

Quarries in the southern California batholith. In San Diego, Riverside, and San Bernardino Counties the various bodies of granitic rock, known collectively as the southern California batholith, are sources of dimension stone. The production of granite in San Diego County from 1898-1963 amounted to approximately 3 million dollars. Two types of granite have been quarried in the country, a pale-gray granodiorite and a 'black granite,' which includes such rock species as hornblende gabbro, norite, and quartz-biotite gabbro. The 'black granite' is in demand for use in monuments and building fronts because of its pleasing black color, fine-grained texture which permits a high polish, and its resistance to weathering. However, the 'black granite' is unusually hard and tough and therefore more costly to quarry and finish than most other California granites.

"Most of these 'black granite" quarries are in residual boulder deposits, whereas the light-gray granite is quarried mainly from massive rock. Distinct joint sets and a poorly developed sheeting structure characterize the massive exposure. The joints intersect at right angles and are spaced from 1 to 10 feet apart. The sheeting surfaces dip gently and generally are parallel to the slope of the land surface and are irregularly spaced from 6 inches to 6 feet apart. Such features are rarely observed in residual bouldery deposits. The boulders have formed chiefly from weathering through expansion and subsequent breaking apart by disintegration.

"The principal dimension stone districts in San Diego County are near Lakeside, Escondido, and Vista. Since 1888, more than 40 quarries have been opened. Fifteen quarries have been active for various periods since 1953, and four were being worked in 1963. The most productive operations in 1963 were those of Escondido Quarries and National Quarries near Escondido. The stone is used for monuments and for making surface plates.

Sandstone (in California)

"Sandstone is a consolidated sedimentary rock composed mostly of mineral or rock fragments that range in size from 1/16 to 2 mm. The most common cementing materials are iron oxide, calcite, silica, and clay. The predominant mineral grains in most sandstones in California are quartz, feldspar, and mica. Some sandstones are composed almost entirely of quartz grains; other sandstones contain 33 percent or more of fragments of dark-colored rocks and minerals and are known as graywacke.

"The usefulness of a sandstone as dimension stone depends largely upon the nature of the cementing material and degree of cemetation. Permanence of color Is desired in a sandstone. Uniformity in grain size, however, is a very desirable feature in sandstone. The ease with which sandstone can be worked, its variety of pleasing colors, and its ability to harmonize with brick and other building material makes it one of the most desirable of the building stones. The principal uses of dimension sandstone are for building stone, flagging, and curbing. An estimated 4 million dollars worth of sandstone has been produced as dimension stone in California since 1887 (Averill and others, 1948, p. 92).

"Sandstone crops out predominantly in the Coast Ranges of northern and central California and the transverse and Peninsular Ranges of Southern California. Almost all of the dimension sandstone has been produced form cretaceous formations.

"The principal centers of past production were located at Sites, Colusa County; Graystone, Santa Clara County; Chatsworth, Los Angeles County; and Sespe Canyon, Ventura County. The main period of sandstone production extended from 1888-1919.

"The principal source of dimension sandstone in the State has been the Upper Cretaceous sandstones near Sites in Colusa County. From 1894 to 1914, these sandstones yielded about 1,186,000 cubic feet of dimension stone valued at $1,448,000. The Sites locality is in a belt of interbedded sandstone and shale that extends along the western margin of the Sacramento valley from the northern boundary of Colusa County southward for 20 miles. In the vicinity of Sites massive sandstone beds, suitable for building stone, are exposed for a distance of 8 miles in a zone three-fourths of a mile wide. The beds range in thickness from 4 to 35 feet, dip approximately 50 to the northeast, and strike northwest. The stone has a blue-gray and buff color and weathers to light brown, is soft and has an even grain. In recent years small quantities have been quarried for use in the San Jose area in Santa Clara County.

Limestone and Marble (in California)

"To the petrologist, marble is a crystalline limestone, but in the stone industry and in the present discussion the term 'marble' is applied to any calcareous rock capable of taking a polish. Some marbles are composed almost entirely of carbonate minerals; others contain such impurities as silica and silicate minerals, iron oxide and iron sulfide minerals, and organic matter. Marble is commonly white, but the iron oxides impart colors of tan, red, or brown, whereas carbonaceous matter causes a gray to black color. Verde antique is a greenish rock composed of serpentine mixed irregularly with calcite.

"Uniform hardness and high resistance to abrasion are desirable qualities in marbles to be used for floor tile, sills, or steps. Marble for exterior purposes should have a low porosity to prevent infiltration of water which may dissolve or discolor the stone. Marble to be used for monuments should present a distinct contrast between chiseled and polished surfaces. The principal uses of dimension marble are as building stone and monumental stone.

"Despite its widespread occurrence in California, marble has been produced commercially in only a few localities, principally in Tuolumne, San Bernardino, and Inyo Counties. From 1887 to 1963 the total recorded production of marble in California was valued at approximately 4 million dollars.

"In 1965, minor amounts of limestone were produced at quarries in Tulare, Santa Cruz, and Solano Counties mainly for use as rubble.

"The Columbia district near Sonora, Tuolumne County, has been the principal source of marble in California. From 1904 to 1942 this district yielded 255,000 cubic feet of marble valued at $700,000. In recent years, the marble has been used as crushed stone.

"The marble in the Columbia district occurs as irregularly shaped masses of dolomite in metamorphosed limestones are exposed belt, approximately 25 miles long and 1 to 5 miles wide, trending roughly northwest. The bedding is generally indistinct and steeply dipping. The marble is a dense, fine-grained dolomite that takes a fine polish. The stone weighs 169 to 182 pounds per cubic foot and has a compressive strength of 25,000 pounds per square inch. The stone most commonly quarried is white with blue veining. A buff stone with reddish veining also was produced.

"From 1896 to 1950, several localities in San Bernardino County yielded 185,388 cubic feet of dimension stone marble valued at $343,076. The main periods of activity were from 1902 to 1909 and 1936 to 1941. The bulk of the early production came from Slover Mountain, near Colton, where a recrystallized limestone of probable Paleozoic age occurs as roof pendants in granitic rocks. The poorly defined limestone strata which strike N. 70 E. and dip 45 E. are more than 2,000 feet thick. These beds are now quarried for use in cement.

Slate (in California)

"Slate is a fine-grained rock produced by the regional metamorphism of clay or shale. Pressure and heat cause the shaly material to partly recrystallize to platy, micaceous minerals in parallel orientation. The cleavage thus produced in sufficiently well developed to allow easy splitting of the rock and is the feature of greatest economic importance. The predominant minerals in slate are muscovite, quartz, chlorite, and carbonaceous matter.

"Approximately $700,000 worth of slate dimension stone has been produced in California since it was first produced in 1880. Peak years were in 1903 and 1906 when approximately one million square feet a year were produced. The output held firm through 1910, but since has been erratic. Small quantities of dimension slate are produced at Chili Bar and Mariposa in the Sierra Nevada.

"Most of the slate production in California has been obtained from the Jurassic Mariposa Formation which is exposed in the western foothill belt of the Sierra Nevada in Mariposa, Tuolumne, Calaveras, Amador, El Dorado, and Placer Counties. The Mariposa Formation originally consisted of shales with minor amounts of interbedded sandstones and conglomerate. Near the close of the Jurassic Period, the formation was folded and locally intruded by granitic rocks, and the shaly material recrystallized into slates and phyllites. The productive slate quarries in California are in a slate-bearing belt that trends northwest from Calaveras to El Dorado County for approximately 65 miles, and ranges from 1 to 3 miles in width. The schistosity strikes northwestward and dips steeply to the northeast, irrespective of the attitude of the original bedding.

Basalt and Related Rock Types (in California)

"In commercial usage and in the discussion to follow the term 'basalt' is applied to any of the dense, fine-grained, dark-gray or black volcanic rocks, including some that geologists refer to under the more specific names of dacite, andesite, latite, and trachyte, as well as basalt in the strict sense. All of them have similar physical properties. The light-colored volcanic rocks are discussed below with the miscellaneous group.

"In California, basalt has been quarried for both paving block and building stone, and an estimated 3 million dollars worth of basalt paving block has been produced (Averill and others, 1948, p. 98). Basalts and related rocks are extensively exposed in many localities in the State. Tertiary and Quaternary basaltic rocks are exposed for hundreds of square miles in the Modoc Plateau, Sierra Nevada, Mojave Desert, Coast Ranges, and Peninsular Ranges provinces.

"Past production of basalt centered around a score of operations in the counties immediately north of San Francisco-Marin, Sonoma, Napa, and Solano.

"The period of peak production years were 1887 to 1891 and 1906 to 1913. More than 50 individual quarries were active from 1864 to 1913. No dimension basalt is presently quarried in California.

Miscellaneous Stone

"Embraced in the general designation of 'miscellaneous stone' is a wide variety of rocks, other than those already discussed, that commonly are attractive enough to be used as dimension stone. These include light-colored volcanic rocks, mica schist, and siliceous limy shale. The important characteristics of these rocks are color, natural appearance, durability, and workability. The colors ordinarily are pleasing shades of off-white, yellow, cream, buff, and pink. The stone should be easily quarried, soft enough to split by hand or by a block-splitting machine, yet durable enough to withstand weathering. Most of the rocks in this group occur as layered rocks with natural partings along bedding planes or along planes of schistosity.

"In California, the principal uses of these miscellaneous stones are as building stone (ashlar, rough block, and rubble) and as flagging. The Pelona Schist in Los Angeles County, and siliceous shale of the Monterey Formation near Carmel in Monterey County were quarried as early as 1927. These and other operations were active intermittently on a minor scale until about 1950, when the building boom created a new demand for stone. By 1963, the value of the annual production of miscellaneous dimension stone in California had increased to $1,109.980. The bulk of production has been from the sedimentary rocks of the Monterey Formation and from the Pelona Schist.

"Monterey 'Shale.' Fine-grained siliceous limy sediments of the Miocene Monterey Formation crop out in the southern Coast Ranges, the Transverse Ranges, and the Peninsular Ranges. The rocks are thinly bedded, dip at low angles in many places, and range from off-gray to buff-brown in color.

"In 1965, the most productive building stone operation in California was at the site of a former diatomaceous earth operation of the Great Lakes Carbon Corp. in the Palos Verdes Hills of Los Angeles. The Palos Verdes Stone Division of this company has directed activities on their 1,000-acre holdings since 1953 when the building stone production begin.

"In Tepesquet Canyon east of Santa Maria in Santa Barbara County, a light-buff to cream, thinly-bedded limy siltstone member of the Monterey Formation has been quarried since 1939. A buff-colored siliceous shaly limestone has been quarried since 1927 near Carmel in Monterey County, but by 1964 production had ceased.

"Pelona Schist. A dark-gray, iron-oxide stained quartz-mica schist of the Precambrian (?) Pelona Schist has been quarried since 1927 at several localities north of Saugus, Los Angeles County.

"Light-colored volcanic rocks. Rhyolite tuff of the Miocene Valley Springs Formation has been quarried in the foothills of the Sierra Nevada since the early 1850's. A buff-colored rhyolite tuff has been quarried at several localities near Placerville, El Dorado County, since 1948.

"Banded, light-gray and purple flow rocks of the Pliocene Sonoma Volcanics have been quarried at several localities near Glen Ellen in Sonoma County since 1928. The rock is a banded riebeckite rhyolite that splits readily along well-defined and closely spaced parting planes which are usually stained with brown limonite.

"Quartzite. A red, iron-oxide stained quartzite is quarried intermittently in small tonnages at Suncrest, San Diego County.

"Field stone. Throughout the State, an undetermined amount of rock is picked off the ground without any quarrying or other treatment. These rocks are used for garden landscaping and occasionally as veneer. Among the rocks thus used as schist, mariposite, pumice, wollastonite, and basalt.

Resource Potential

"The outlook for expansion of the dimension stone industries is fair. The market for monumental stone has been growing, and the merits of using natural building stone are being increasingly recognized by architects, builders, and the general public. However, future development in California will continue to be restricted by the competition from foreign and eastern United States sources."

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