Lynchburg uses sand from Virginia

GLASS-SAND RESOURCES OF VIRGINIA.

By Thomas L. Watson.

Introduction.

The resources of Virginia in quartz sand or its hard rock equivalents suitable for glass-making are very great. Quartz in the form of sand or hard rock desirable for purposes of glass manufacture occurs in each of the three major physiographic divisions of the State, and is produced at present in each province for such use. In many localities the sandstones and quartzites are of exceptional purity. Many of them are favorably located for quarrying and to lines of transportation, and are near to abundant supplies of high-grade coal.

There are four plants in Virginia engaged at present in the manufacture of glass, located at Alexandria, Richmond, Lynchburg, and Salem, with a fifth one expected to begin operating shortly at Norfolk. Of the four producing plants two derive their supply of sand from Virginia while the others obtain their supply from West Virginia. The total production of glass-sand, which is not very large, is consumed within the State.

Kinds of Material.

The kinds of silica found in Virginia in quantity and of sufficient purity (see table of analyses on page 797) to be utilized in making glass include (1) quartz sand, (2) sandstone and quartzite, and (3) vein quartz including some pegmatite occurrences. These materials probably have not equal value for glass-making and, under present conditions, some of them may not be usable, although well located and occurring in quantity and of sufficient purity. The distribution and character, including analyses of these materials, are briefly summarized below by physiographic provinces.

Coastal Plain Province.

The Coastal Plain or Tidewater Virginia, the easternmost province, comprises about one-fourth the total area of the State. The major streams which cross it are navigable for the entire width of the province and with the lines of railway afford excellent transportation facilities.

The Coastal Plain province is composed of loose or locally indurated sediments, of which sands of different kinds form an important part. The sands vary greatly both as to size of grain and purity. In many localities they consist of pure quartz grains but more often they are admixed with more or less clay and iron oxide, and may carry small grains of other minerals than quartz, such as magnetite, ilmenite, etc., but not in harmful amounts in some of the deposits. Glauconite, an iron-bearing mineral, is usually an abundant constituent in many of the Eocene sands which are of little or no value for glass manufacture when this mineral occurs in appreciable quantity.

The better grades of the Coastal Plain sands have been employed in a variety of uses but in greatest quantity for building purposes. Some of the sands are pure enough to be utilized for glass-making, but thus far they have been so employed only to a very limited extent.

Extending from Cape Henry southward into North Carolina, sands dune are prominently developed along the coast, forming a conspicuous feature of the coastal topography. The material is loose beach-sand accumulated landward by the wind. Small shipments of this sand in the vicinity of Cape Henry are made at present to one of the Virginia plants for glass-making. Because of their extent and favorable location (only a few miles east from the city of Norfolk), these sands are worthy of careful investigation in order to determine their desirability for glass manufacture.

Extending along the western margin of the Coastal Plain, from Fredericksburg northeastward to the Virginia boundary, is a belt of Cretaceous sands sufficiently indurated locally as to have been formerly quarried for building stone. They are essentially light-colored sands, composed in places almost entirely of pure variablesize quartz grains, but they frequently contain much kaolinized feldspar. It seems probable that, in certain localities within this belt, the sands might be utilized to advantage in the manufacture of at least the lower grades of glass. So far as we are aware, however, no attempt has yet been made to use them.

Piedmont Plateau Province.

As defined at present, the Piedmont Plateau province comprises that part of Virginia included within the fall belt on the east and the southeast slope of the Blue Ridge Mountains on the west. It is composed dominantly of a complex of the older crystalline silicious rocks, although several areas of Triassic rocks are comprised within its limits. Belts of metamorphosed sediments yielding crystalline limestones, quartzites, and slates of early Paleozoic age also occur.

Within the Piedmont province are distributed several kinds of highly quartzose materials, including quartzite, quartz veins, and pegmatite bodies, some of which are sufficiently pure and otherwise desirable for glass manufacture.

The stream sands deposited along river courses in the Piedmont province are usually too impure to be seriously considered for purposes of glass manufacture. Most of the quartzites are likewise too impure to be used in glass-making, since they may carry large but varying amounts of either micaceous minerals, feldspar, epidote, or iron oxides (chiefly magnetite and ilmenite, and in places hematite). In some localities, however, the quartzites are entirely white in color; arc composed almost wholly of pure quartz, with inappreciable amounts of other minerals; and could be used to advantage in glass-making.

Only one locality in the Piedmont Plateau is yielding quartzite or its disintegration product, quartz sand, at present for the manufacture of glass. A white quartzite of Lower Cambrian age, located near Stapleton in Amherst County, about 12 miles north of east from the city of Lynchburg, is being utilized by the Lynchburg plant for the making of glass. A partial analysis of a sample of this quartzite is given in the table of analyses on page 797. The sample yielding the analysis, however, contains, besides quartz, considerable white, silvery mica (sericite). Other analyses of samples of the quartzite indicate more than 95 per cent of silica, with only a trace of iron. Fusion tests made on a sample of the rock yielded a very satisfactory grade of glass. Similar quartzites of equal purity and of the same geologic age are found in other localities in the Piedmont province, but have not yet been drawn on as a source of raw material for glass manufacture.

Table I. — Analyses Of Virginia Glass Sands.º

Piedmont Plateau Province.

º Nos. 1 and 2. Cambrian quartzite near Stapleton, Amherst County, Virginia (S. D. Gooch, analyst).

No. 3. Silex (vein quartz), Madison Courthouse. Madison County, Virginia (S. D. Gooch, analyst).

No. 4. Silex (vein quartz), 1 mile east of Boyd Tavern, Fluvanna County. Virginia (S. D. Gooch, analyst).

No. 5. Silex (vein quartz), near Scottsville, Albemarle County, Virginia (J. B. Weems, analyst).

Nos. 6 and 7. Cambrian (Erwin) sandstone from Locher place (Glasgow Clay Products Company), near Glasgow, Rockbridge County, Virginia.

No. 8. Silurian (Clinch) sandstone near Kermit, Scott County, Virginia (S. D. Gooch, analyst).

No. 9. Silurian (Massanutten-Tuscarora) sandstone, Catawba Mountain, 9 miles north of Salem, Virginia. (By courtesy of the Salem Glass Company, Inc., Salem, Virginia.)

No. 10. Catawba Valley sand (Massanutten-Tuscarora sandstone), 9 miles north of Salem, Virginia (H. H. Hill, analyst).

No. 11. Cambrian (Erwin) sandstone, C. & O. railroad quarry, east of Basic, Augusta County, Virginia (S. D. Gooch, analyst).

Large bodies of exceptionally pure quartz are widely distributed over many parts of the Piedmont province which, judging from the analyses given on page 797, could be utilized in many cases to advantage in glass-making. The quartz of the numerous pegmatite bodies occurring in the Piedmont province is probably of less importance because of the size of the pegmatites and the irregular distribution of the quartz in them, in this connection than either the quartzites or the vein quartz, although the quartz can be readily separated from the feldspar, both of which are used in the manufacture of pottery.

Mountain Province.

This province embraces the western part of the State; its eastern boundary is the southeast slope of the Blue Ridge and its western limits mark the boundary between Virginia, West Virginia, and Kentucky. It includes the following topographic divisions: (1) The Appalachian Mountains to which the name Blue Ridge is applied in Virginia; (2) the Appalachian Valley which is divided lengthwise into an eastern part known as the Great Valley and a western part referred to as the Valley Ridges; and (3) the Appalachian Plateau, the Virginia portion of which includes the extreme southwestern part of the State adjacent to Kentucky and West Virginia. The Appalachian Mountains and Appalachian Valley provinces extend in a general southwest direction over 300 miles from the northern to the southern boundary of the State.

Of the subdivisions of the Mountain province the Appalachian Valley, which is composed of folded Paleozoic sedimentary rocks ranging from Cambrian to Carboniferous (Mississippian) in age, contains vast glass-sand resources in the form of sandstones and quartzites. Notwithstanding this fact there is only one Glass-making plant operating at present in this part of the State.

The formations of the Appalachian Valley that either contain abundant supplies of silica suitable for glass-making or are worthy of careful investigation for such use may be tabulated in the order of their age, beginning with the oldest, as follows:

Cambrian:

1. Unicoi sandstone which includes the Weverton sandstone and Loudoun formation in northern Virginia and adjacent parts of West Virginia.

2. Erwin quartzite which includes the Antietam sandstone of northern Virginia and adjacent parts of West Virginia and western Maryland.

Silurian:

3. Clinch sandstone which includes the Tuscarora (Massanutten) sandstone of west-central and northern Virginia, and adjacent parts of West Virginia.

4. "Rockwood" formation.

Devonian:

5. Oriskany ("Monterey") sandstone.

Mississippian:

6. Pocono sandstone which includes the Price sandstone of southwestern Virginia.

The sandstones of each of these formations have wide general distribution in the Appalachian province, but owing to their greater purity in many localities the sandstones of the Cambrian and Silurian systems must be considered the most important sources of silicious material for glass manufacture. As indicated from the analyses on page 797 and from the descriptions below, these sandstones are remarkably free from impurities in places, especially iron, which is essentially absent.

Cambrian Sandstones. — The principal development of the Cambrian sandstones in Virginia, including the Unicoi (Weverton and Loudoun of northern Virginia), and Erwin quartzite (Antietam of northern Virginia) is along the west foot of the Blue Ridge or at the border of the Appalachian Valley and the Appalachian Mountain (Blue Ridge) provinces. In their normal sequence the Unicoi and Erwin are separated by the Hampton (Harpers) shale, which formation is estimated to be at least 400 feet thick in northern Virginia and 600 to 800 feet in southwestern Virginia. Because of their greater resistance to weathering the sandstones and quartzites of these formations form low knobs and high ridges of considerable prominence in places in front of the main Blue Ridge. "The Erwin quartzite is one of the most conspicuous formations in the region because it makes such prominent rocky ridges and because of its conspicuous white color."¹ Over much of the region the beds of these two formations, especially those of the Unicoi, are of no value as glass sands, but in many localities the massive white to gray beds of sandstone are of sufficient purity to be of importance as a source of sand for glass-making.

The Unicoi formation which directly overlies the crystalline rocks, includes sandstones, arkoses, conglomerates, and quartzites. "In the northern part of the region these beds range from soft arkose through harder arkosic sandstones to hard, gray sandstone and dark, ferruginous quartzite, and associated beds of slaty, argillaceous sandstone. Some of the basal beds have rounded grains and small pebbles of quartz which are usually clear and transparent, though some have an opaline-blue color. Besides quartz there are grains of feldspar, generally chalky white from weathering, and considerable clay and iron oxide."²

The Unicoi formation in northern Virginia is probably not less than 1,750 feet in thickness and is probably thicker in southwestern Virginia. Except in northern Virginia and possibly in some places in southwestern Virginia, the Unicoi sandstones are not generally of glass-making quality. East of the main Blue Ridge in Loudoun County some beds of the Unicoi (Weverton) are very white and pure, being composed almost entirely of quartz grains and apparently could be used to advantage in glassmaking.

The Erwin quartzite is a massive white rock, the outcrops of which make prominent ridges throughout the region, and in northern and central-western Virginia, especially, it forms a potential source of unlimited supplies of glass sand. "The western foothills of the Blue Ridge over most of the region are composed of this rock, and it also caps many of the ridges of an inner row where there are several lines of ridges. In the northern part of the area the formation is generally composed of three massive cliff-making ledges separated by thinner bedded sandstones . . . "The cliff-making ledges consist largely of massive beds of dense, white quartzite, some of which are 15 to 20 feet thick without a visible trace of bedding.³ Analyses of the Erwin quartzite are given in the table of analyses on page 797.

Over much of the southwest Virginia region, especially in Smyth and Wythe counties, white, hard, massive, vitreous quartzite is least abundant of the beds composing the Erwin, and hence the value of the Erwin sandstone over this part of the State is of less importance as a source of supply of glass sand than in the central-western and northern parts of Virginia.

Silurian Sandstones. — Of the two sandstones of Silurian age the Clinch and the coarse, white sandstone next below the Clinch, or the top member of the "Rockwood" formation (Clinton), the former is much the more important for glass-making.

The Clinch sandstone of southwestern Virginia and its equivalent Tuscarora (Massanutten) sandstone of west-central and northern Virginia, is a massive, coarse, white sandstone or quartzite that forms most of the more prominent valley ridges in southwest Virginia. It ranges up to 300 or 400 feet in thickness and is prominently developed in Clinch Mountain which is the most conspicuous of the Valley Ridges. Under favorable conditions the sandstone weathers in places to a white sand composed almost entirely of pure quartz grains.

The glass plant located at Salem, Virginia is using the equivalent of the Clinch sandstone (Tuscarora) which is derived from Catawba Mountain, about 9 miles from Salem, in the manufacture of glass. The rock is crushed and screened and is then ready for use. An analysis of this rock is given in the table of analyses on page 797.

At or near Kermit, a station on the Carolina, Clinchfield & Ohio railroad, Scott County, is one of the most important localities in the State from which a high-grade glass sand of excellent quality can be obtained for glass-making. Here the Clinch sandstone has good development in beds of exceptional purity. The sandstone is composed almost entirely of moderately rounded, fairly uniform-size grains of quartz of great purity, the total ferric oxide amounting to only 0.014 per cent, as determined by the Pittsburgh Branch of the Bureau of Standards on a sample submitted by the writer. Fusion tests made with a second sample of the sand gave an excellent color, even without the use of a decolorizer. This quality of sand should be of considerable interest to manufacturers of optical glass and of other kinds of fine glass. (See table of analyses on page 797 for an analysis of the Clinch sandstone near Kermit.)

Devonian Sandstone. — The Oriskany ("Monterey") sandstone has wide distribution in western Virginia, chiefly in the Valley Ridges province where owing to the hardness of the rock its outcrops usually form knobs and ridges that are often prominent. The formation, which may range up to several hundred feet in thickness, is composed of a hard, fine- to medium-grained calcareous sandstone of light buff to bluish gray color. The quartz grains are cemented by lime carbonate and under favorable conditions the rock weathers readily to sand and loose fragments. The Oriskany sandstone has not been quarried in Virginia for glass-making, but in some localities in the State where the rock is essentially free from iron and other injurious impurities it seems worthy of investigation for such use. It is well known that this sandstone is quarried and used in Pennsylvania and West Virginia for glass-making and in the latter State it is the most important glass-sand horizon yet developed.

Under this heading are included sandstones, mostly unfossiliferous, which may be of Salina (Silurian) age, and which in one locality at least are of marked purity. In a section measured by Mr. G. W. Stose, along the Chesapeake and Ohio railroad on the east side of James River gap through Rathole Mountain, Eagle Rock, a 55-foot thickness was shown of a pure white, sugary, granular sandstone, of probable Salina age, which crumbles to white sand on weathering. The purity, thickness, and location of this sandstone immediately on the railroad render it especially worthy of careful investigation for probable use in the manufacture of the better grades of glass. Some of the sandstone beds below this one in the section are also quite pure and of considerable thickness, and will probably prove to be of value for the same purpose. The Tuscarora sandstone of hard, white to gray color beds, and alternating with soft, white sandstone beds, poorly exposed, are shown in the same section. These sandstones (Salina? and Tuscarora) are worthy of careful examination and analysis to determine their desirability for glass-making.

Mississippian Sandstone. — The Pocono sandstone of west-central and northern Virginia and its equivalent, the Price sandstone of southwestern Virginia, is a hard, ridge-making rock that is subject to considerable variation in composition in different localities. It frequently carries thin beds of coal near the top and is apt to be conglomeratic in the lower or basal portion. Because of its iron content and the presence of other impurities, together with non-uniformity of texture as generally shown in most of its outcrops over southwest Virginia, the Price sandstone has no value for glass-making, but in west-central Virginia its equivalent, the Pocono, is developed as a heavy bedded white-to-buff quartzite of apparently sufficient purity as to encourage the belief that in some places at least it might be used.

University Of Virginia.

¹ Va. Geol. Surv., Bull. 17, 17 (1919).

² Ibid., 17, 13 (1919).

³ Va. Geol. Surv., Bull. 17, 15 (1919).