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Production

During the period 1945-64, sandstone ranked first, being 56 percent of the dimension-stone tonnage quarried in Appalachia; in value it ranked second, accounting for 31 percent of total sales.  During the same period, 44 percent of dimension sandstone quarried in the United States was produced in Appalachia.  Quantities and values of annual production in Appalachia and the United States for the 20-year period are presented in table 72.

Production of sandstone (dimension stone), 1945-64

Table 72.  Production of sandstone (dimension stone), 1945-64  Source: U.S. Bur. Mines)

The principal producing States in Appalachia during the last two decades have been Ohio, Tennessee, New York, and Pennsylvania.  Some production was reported from West Virginia, Georgia, North Carolina, Kentucky, Maryland, and Alabama.

Uses of sandstone produced in Appalachia for 1963 and 1964 are shown in table 73.  About 76 percent of the production in both years was sold for building stone; the remainder was used for curbing and flagging.

Table 73. Sandstone (dimension stone) sold or used by producers

Table 73.  Sandstone (dimension stone) sold or used by producers
in the Appalachian Region, by uses, 1945-64  Source: U.S. Bur. Mines)

Granite

A wide variety of crystalline igneous rocks are used for dimension stone because of their great strength, durability, coloration, and high polishing characteristics, but commercially all varieties are called granite.  The light-colored varieties include true granite, granodiorite, quartz monzonite, and related rock types, whereas dark-colored varieties, commonly called "black granites" include diorite and gabbro.  True granite is a visibly granular rock consisting of feldspar, quartz, and mica or hornblende.  Granodiorite and quartz monzonite differ from true granite only in the kinds and amounts of feldspar contained in the rock.  Quartz monzonite, for example, contains as much or more sodic feldspar as it does potassic feldspar.  Diorite and gabbro contain varying amounts of both sodic and calcic feldspars as well as more abundant ferromagnesian minerals such as hornblende, augite, and olivine, giving a darker color.  Crystalline rocks in which the alignment of certain minerals, commonly mica or hornblende, is roughly parallel because of metamorphic effects are called gneiss.  The term "granite gneiss" or simply "gneiss" identifies rock of this type.

Granite is one of the hardest stones used for building purposes; consequently, it is expensive to quarry and shape into usable forms.  Most granite masses contain parallel systems of joints or cracks and, to keep costs at a minimum, sites for the production of stone are selected where joint systems facilitate quarrying operations.  The most favorable condition for quarrying is one in which the joints occur in three systems, approximately at right angles to each other and spaced several feet apart.  Where joints are too numerous and closely spaced, the granite will not yield sound blocks large enough for building purposes.  The stone generally splits in certain directions with greater ease than in others.  The direction of easiest splitting is known as the rift.  A second, less-marked tendency to split, generally at right angles to the rift, is known as the grain.  A well-defined rift and grain are of great assistance to the stonecutter in shaping massive blocks.

Granite Belts and Areas

Granite and related rock types occur throughout large areas in the Piedmont province of southeastern Appalachia, and most of the granite produced in Appalachia for building purposes has come from this region.  The Piedmont province is almost entirely underlain by Precambrian and Paleozoic metamorphic rocks, chiefly gneiss and schist, that have been intruded by various-sized masses of granite.  Within this igneous and metamorphic terrane, many areas contain large deposits of both granite and gneiss suitable for use as dimension stone.  Most quarry sites, however, are located within the granite masses forming rather narrow northeast-trending belts (fig. 60).  Selection of sites is further guided by the distribution of a thick residual mantle of earthy clay and decayed rock called saprolite.  Where saprolite is thick, the expense of removal to expose fresh rock is generally prohibitive.  Sites are selected, therefore, in areas where the saprolite is thin or absent.

The locations of some areas containing granite quarries are shown in figure 60 and identified in table 74. Four of these areas, selected as having representative types of commercial granite, are briefly described. 

Areas containing dimension granite quarries

Table 74.  Areas containing dimension granite quarries.

Surry County, N.C.-Granite occurs in two narrow belts trending northeastward across the eastern half of Surry County.  The rest of the county is underlain by various types of gneisses and schists.  Deep weathering has rendered much of the granite unsuitable as a convenient source of dimension stone, but at Mount Airy (loc. 26), fresh unjointed granite is exposed for about 5,000 feet along the crest of a rather conspicuous hill (Councill, 1954, p. 45).  This granite, a very light gray to almost white, medium-grained stone composed of feldspar, quartz, and mica, has been extensively quarried since 1904.  Blocks of stone are obtained by lifting layers of granite, and subdividing them into blocks by the plug and feather method, as described in detail by Councill (1954, p. 51-53).  The blocks are slabbed, shaped, and polished in nearby shops for use in building and trimming mausoleums, in bridge construction, as architectural stone, and for curbing.  they are also used for statuary and monuments.  The quarries of this area lead the Nation in output of stone used in Mausoleums (Councill, 1954, pg. 45).

Spartanburg County, S.C.-According to Sloan (1908, p. 198), a gray medium-fine-grained biotite granite with excellent working qualities and susceptible to high polish has been quarried near Pacolet (fig. 60, loc. 31).  This granite underlies an area of at least 100 acres, and has been extensively quarried for use in monuments.

Anderson County, S.C.-Biotite granite gneiss, ranging in color from dark gray with a reddish cast to bright gray is reported by Sloan (1908, p. 177) to have been extensively quarried in the vicinity of Pendleton (fig. 60, loc. 35) and used to make culverts, abutments, and piers.  The granite has good working qualities under chisel and chipping hammers and takes a fine polish.

Gwinett County, Ga.-An extensive belt of highly contorted biotite granite gneiss begins just south of the border of Appalachia in north-central Georgia, extends northeastward from the southern half of the county, and terminates in Barrow County.  Within this belt the granite gneiss is exposed both as a surface pavement and as dome-shaped masses that rise in places several hundred feet above the surrounding lowlands.  Many quarries throughout the belt have produced dimension stone, particularly at Winder, Bay Creek, Snellville, Centerville, and Lithonia-Pine Mountain (Fig. 60, loc. 39-44).  According to Watson (1902, p. 142) the first stone quarried in the area was at Pine Mountain, in 1883.  Herrmann (1954, p.8) described the stone as being medium grained, extremely hard, gray white and showing banding due to concentrations of light- and dark-colored minerals in alternating bands ranging in thickness from one-tenth to one-half inch.  The stone is well suited for general building purposes and for curbing because of is ease in quarrying and ability to withstand weathering.

Production

Granite constituted 12 percent of the tonnage and 9 percent of the value of Appalachian dimension-stone production from 1945-1964.  The Appalachian output of 678,000 tons during this period amounted to 6 percent of the total dimension granite quarried in the United States.  Quantities and values of annual production in the United States for the 20-year period are given in table 75.  Annual Appalachian production is withheld in order not to disclose individual company data.  Leading producing States in Appalachia were North Carolina and Georgia.  Of the 1964 Appalachian production, 52 percent was sold as building stone and the remainder as curbing, flagging, monumental stone, and paving blocks.

Production of granite (dimension stone), 1945-64

Table 75.  Production of granite (dimension stone), 1945-64  (Source: U.S. Bur. Mines)

Slate

Slate, consisting essentially of quartz and silicate minerals, is a microgranular crystalline rock derived by metamorphism of shale.  Slate's distinguishing characteristic is its tendency to cleave easily along nearly parallel and very closely spaced plane; this is the main basis for its industrial value.  Other important properties are color, hardness, toughness, and electrical and chemical resistivity.  Slate is used either as a dimension stone or in crushed or finely ground form.  Dimension shapes are used for roofing, for blackboards, for mounting electrical equipment, and as "mill stock" for making stair treads and risers, flooring and flagstones, building-facing panels, mantles and hearths, sinks and drainboards, grave vaults and covers, table tops, and for decorative stone of various kinds.  Slate crushed to granule size has been used to coat composition roofing and siding, and presently is used for surfacing tennis courts and driveways.  Finely ground slate is used as inert filler in a variety of products ranging from paint to rubber and in abrasive soaps and polishes.

The color of slate is of considerable commercial importance.  The colors most desirable for roofing are deep brick red, grayish purple, olive green, gray green, dull-bluish green, brown, or mottled in various color combinations.  Color differences are due to the presence of various mineral constituents, such as hematite in red slate, chlorite in dark-green slate, sericite in light-green and gray slate, and carbon in black slate.  In deposits of slate, cleavage, grain, shear zones, and joints are of primary importance.  Cleavage determines how well the slate will split into large very thin slabs such as blackboards.  The grain, a plane of breakage usually at right angles to the cleavage, determines the ease with which usable blocks of slate can be broken out of a quarry.  Widely spaced joints are an aid in quarrying, but numerous shear zones and closely spaced joints generally make the slate worthless as dimension stone.

In the region of Appalachia, most slate occurs in long sinuous belts associated with other metamorphic rocks, chiefly argillite, phyllite, schist, quartzite, and marble.

Valley and Ridge Slate Belt

Most of the slate in Appalachia occurs in a long narrow belt which extends from Unicoi and Washington Counties, Tenn. southwestward through Georgia, and into Bibb and Chilton Counties in central Alabama (fig. 60).  This belt coincides in a general way with the eastern boundary on the southeast along most of its length by major thrust faults, and is delineated on the northwest by a somewhat arbitrarily drawn line, west of which slaty cleavage is absent or poorly developed in the rocks.

Slate deposits within the Tennessee part of the belt occur in the Ocoee Series of Precambrian age in Blount, Monroe, and Sevier Counties.  The slate in Blount County is light to dark bluish gray, pale green and pale purple, and even grained, with good cleavage and moderate strength.  Most cleavage surfaces are rough and lusterless.  Virtually all of the former workings in Blount County are now included in the Great Smoky Mountains National Park.

Several quarries have been opened in Monroe County, but most of the slate appears to have been used locally.  This slate is micaceous and exhibits various colors and types of cleavage including dark-bluish gray with lustrous ribboned cleavage faces, dark-purplish gray and green with smooth lusterless cleavage faces.

Sevier County slate has not been mined and few data are available about it.

In the Georgia part of the belt, slate has been quarried from two separate formations; the Conasauga Formation of Cambrian age in Bartow County, and the so-called "Rockmart Slate," a lens within the Chickamauga Limestone of Ordovician age (Hates, 1902) in Polk County.  The slate-producing area in Bartow County is nearly 5 miles wide and, although it extends northward into Gordon and Murray Counties (Shearer, 1918, p. 99), most slate has been produced from the vicinity of Fairmount (fig. 60, loc. 52) near the Gordon County line where the slate is green.  Until World War I, the slate was quarried extensively for roofing material.  Later, according to Furcron (1964-65, p. 20), the use of green slate for roofing granules caused a revival of the industry, and the deposits have provided a steady flow of slate granules and flour.  However, dimension slate is no longer produced.

The slate-bearing areas in the vicinity of Rockmart, Polk County (fig. 60, loc. 53), are bounded on the southeast by a large thrust fault.  The commercial deposits, consisting of very dark bluish-gray slate with smooth to rough and uneven cleavage, lie in a zone a few miles wide.  The material within a half mile of the bounding thrust fault is badly crumpled and schistose (Shearer, 1918, p. 57) and therefore unsuitable for use as a dimension stone.  Material more than a few miles away from the fault has imperfect slaty cleavage that makes it unsuitable for most uses.  The slate is weathered to depths ranging from 15 to more than 40 feet.  Quarrying of Rockmart slate began about 1850 (Furcron, 1964-65, p. 29), and most of it was used as roofing material.  Since then, the quarries have been worked intermittently, but none of the slate is now used for dimension stone.

Slate-bearing areas in the Alabama segment of the belt, chiefly in Talladega, Shelby, and Chilton Counties (fig. 60), have been prospected and some material has been quarried for local use.  Jones (1926) reported that the slate appears to be of good quality.  The slate occurs in several different formations:  the Talladega Slate of Precambrian (?) to Carboniferous (?) age, the Weisner and Rome (Montevallo) Formations of Cambrian age, and the Chickamauga Limestone of Ordovician age.  The best deposits occur in the Weisner Formation in the southwestern part of Talladega County, and in the Rome (Montevallo) Formation in Chilton County.  Butts (1940b) reported the presence of rock suitable for use as roofing material in the Waxahatchee Slate in Shelby and Chilton counties.  He described it as light gray with good cleavage but containing numerous closely spaced joints.

West Virginia Slate Belt

Dark-gray to black carbonaceous clay-slate of doubtful quality occurs within a belt of Martinsburg Shale of Ordovician age in Berkeley County, W. Va.  According to Dale (1906, p. 119), the northeast-trending belt is 14 miles long and 2-3 miles wide.  The slate is generally unsuitable for most uses but some may find use as mill stock items for inside use.

Pennsylvania Slate Belt

The Pennsylvania slate belt, described by Behre (1927, 1933), Ashley (1931), Stone (1932), and B. L. Miller and others (1939, 1941), trends northeastward parallel to, but, for the most part, just outside the southeastern boundary of the Pennsylvania part of Appalachia.  The slate, formed within the Martinsburg Shale, has been extensively quarried.  The belt is one of the largest slate-producing regions in the United States.  A small part extends into Carbon County where according to Dale and others (1914, p. 108-109), dark-bluish-gray slate with finely banded texture and rough lusterless cleavage surfaces has been quarried for roofing slate and mill stock.

Other Slate-Bearing Areas

Sullivan and Washington Counties, Tenn.-Two areas containing small deposits of slate lie north of the Valley and Ridge slate belt, one in Sullivan County, the other in Washington County (fig 60).  Both deposits are in the Athens Shale of Ordovician age.  The slate is very dark gray to black with fair cleavage  (Dale and others, 1914, p. 118-119).

Fannin County, Ga.-Several quarries have produced slate for flagstones and crushed rock from the Nantahala Slate of early Paleozoic (?) age and the Brasstown Schist of Cambrian age, in the eastern part of Fannin County (fig. 60). The slate is greenish gray to grayish black, strongly banded and ribboned, and relatively coarse grained.  It has good slaty cleavage and breaks readily into thin sheets many feet across (Hurst, 1955, p. 50-51, 127).



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