ing, blackboards, school slates, electric switchboards, table tops, wainscoting and vats. Probably the greatest demand at present, aside from roofing purposes, is for switchboards.

Occurrence. "The area in which the slates of Arkansas are located includes a part of the Ouachita Mountains and extends from near Little Rock westward to near Mena. Its length is about 100 miles and its average width probably is about fifteen miles. It includes parts of Saline, Garland, Montgomery and Polk Counties.

"There are five formations of the Ouachita Range that contain slate. These are the Ouachita shale, the Polk Creek shale, the Missouri Mountain slate, the Fork Mountain slate and the Stanley shale. Only the three last named have been prospected to any extent, and most of the prospecting and developing has been done in the Missouri Mountain slate.

"The Ouachita Shale.-The Ouachita shale is the surface rock about Black Springs and elsewhere in the Caddo Basin, Montgomery County. Its area over the Ouachita Range is not known, but it is greater than the area of all the other slate formations combined. As its name implies, it is mainly a shale, there being usually no indication of slaty cleavage; but in places slaty cleavage is well developed, and in such parts is conspicuous in the stream beds, by the road side, and in other places where the formation is exposed. Some of this slate is sufficiently indurated for roofing slate, but usually it is too soft to long withstand the weathering agencies. Also, it is in all places where observed so closely joined as to prevent the quarrying of blocks of commercial size. Besides, its banded or "ribbon" structure would prevent its being desirable commercial slate, even though it possessed all the other requisite qualities.

"The Polk Creek Shale. The Polk Creek shale is only about 100 feet thick, and this, with the folded nature of the region, causes it to outcrop as narrow belts, which usually are found along the bases of the mountains. This, like the formation above described, is commonly a shale, though locally slaty cleavage is well developed in it. In places this slate is banded, but in others it is of a uniform black color, hard, possessing a high metallic ring and containing large numbers of graptolite fossils. Jointing is very common in this, in both the shale and the slate. On account of the comparatively small amount of this formation in which slaty cleavage is well developed, and the frequency of the joints, it does not give much promise as a producer of commercial slate, though there may be parts from which such could be secured.

"The Missouri Mountain Slate. This is the formation in Arkansas that has been most prospected for slate. While it does not enter into the minor folding of the region, as does the Polk Creek shale, it, like the formations above, partakes of the principal folding. It

is widespread over the area, and often outcrops near the mountain bases, though it may be found high up on the slopes, or even in notches of the crests of the ridges.

"This slate has been rather extensively prospected all the way from Board Camp Creek in Polk County eastward to the Ouachita River, in Garland County. The point at which it has been most extensively worked is Slatington, Montgomery County, though there are other prospects in it of consideráble magnitude. The wide extent to which it has been prospected is due, not only to the promise it has given as a source of commercial slate but to the favorable location and nature of its outcrops, which usually are in bluffs, and well up on the mountain slopes. It varies in thickness from a maximum of about 300 feet to a minimum of fifty feet or less. The thickest portion is along the central line of the Ouachita Range, from which it thins out southward and probably northward.

"This formation produces both red and green slate. Though both kinds may and often do occur in the same quarry, the red is predominant. It is a clay slate of remarkable homogeneity, sandy or other impure layers being absent. In color it varies from a scarlet to a dark red, but that of any particular quarry is likely to be uniform. In exposed surfaces it presents a rich, usually pleasing appearance. On account of its' homogeneous nature, no traces of the original bedding are to be seen.

"In most parts this slate is intersected by numerous joints that run in all directions, but if favorable places are selected these are not so common as to prevent the quarrying of large blocks. The slate cleaves with fairly even surfaces and can readily be split into sheets a quarter of an inch thick or less.

"Because of its softness and homogeniety this is altogether a desirable slate to work. It splits, saws and planes easily, and soon takes a polish on the rubbing-bed. But in the process of drying, after having been taken from the rubbing-bed, it is liable to check, and the amount thus lost greatly reduces the profit of working it. If some method of working can be devised that will avoid this checking, the slate industry of the State will become an important and paying

one.

"The Fork Mountain Slate.-This slate lies normally above the Arkansas novaculite, but, due to overturning, it frequently occurs beneath this formation on the mountain slopes. On account of an unconformity at its top the formation is not everywhere present, and for the same reason it varies greatly in thickness at the different places where it is known to occur. Its maximum thickness has not yet been ascertained, but in Section 5, Township 4 south, Range 27 west, where it outcrops well upon the mountain slope, it is known to exceed 100 feet.

"This is a hard slate, usually gray in color, though portions of it on weathered surfaces are green or chocolate. Thin, sandy or quartzitic layers are quite, frequent. The cleavage usually is well developed and occurs at all angles to the bedding planes. 'Ribbons' not infrequently occur. It has great strength and toughness and is highly sonorous. In most places jointing is so frequent as to render the slate worthless, but it must not yet be concluded that exploiting will find it universally so. Prospectors should not neglect this slate. While it never would do for milling purposes, if found sufficiently free from joints and sandy seams it would make shingles.

"The Stanley Shale. This formation, as the name implies, is almost everywhere a shale, no slaty cleavage having been developed in it. But in some parts of the closely folded synclines of the Quachita Range it is altered into true slate. This slate has been rather extensively prospected near Slatington, and at several places in the southeastern part of Polk County. It is blue to black in color, and where the cleavage is best developed it is remarkably fine, permitting the slate to split into very thin sheets with smooth, beautiful surfaces. With the exception of the quarry near Slatington, and one east of Bear, belonging to the Ozark Slate Company, none of any size has been opened in this formation. This formation does not give much promise of producing commercial slate.

:

"Production. As early as 1859 a slate quarry was opened northwest of Little Rock. A company was formed to quarry this slate for roofing purposes, but it was found incapable of standing the weather. Many years ago a quarry was opened near the mouth of Glazierpeau Creek, twelve miles northwest of Hot Springs, but no reliable report of this slate having been utilized has been secured. From 1885 to 1908 several quarries were opened up in the western part of Pulaski County and the eastern part of Saline County, and from some of these a small amount of roofing slate was shipped.”

In 1908 milling slate was put on the market by the Southwestern Slate & Manufacturing Company. Value of production from 1891 to 1912, according to U. S. Geological Survey figures follows:

Producers. There is no slate being quarried in Arkansas at the present time (1927).

1.

Bibliography of Slates

1904

Dale, T. N., "Note on Arkansas Roofing Slates."-Bulletin No. 225 of the U. S. Geological Survey, pp. 414-416. Now out of print, but may be consulted in public or scientific libraries.

1906

2.

Dale, T. N., and Eckel, E. C., "Slate Deposits of the United States." -Bulletin No. 275 of the U. S. Geological Survey, p. 51. Now out of print, but may be consulted in public or scientific libraries.

3.

1909

Purdue, A. H., "The Slates of Arkansas."-Annual Report of the Arkansas Geological Survey for 1909, Vol. I. Obtainable from Arkansas Geological Survey, State Capitol Building, Little Rock, Ark.

1914

4.

Eckel, E. C., "Chemical and Microscopical Analyses of Arkansas Slates."-Bulletin No. 586 of the U. S. Geological Survey, pp. 62-65. Obtainable from U. S. Geological Survey, Washington, D. C., for 50c.

SOAPSTONE

Composition.-Soapstone is a hydrous magnesium silicate or an impure form of talc. The composition of soapstone is variable and its talc content is sometimes as low as 50 per cent. It is a term loosely applied to rocks with a soapy feel and to many soft, easily cut rocks in which chlorite predominates over shale.

Soapstone as the term is usually employed means a dark green or bluish gray rock composed principally of talc and containing other minerals such as chlorite, mica, pyroxene, tremolite, etc. It is formed either from the alteration of eruptive rocks or from magnesian sedimentary rocks.

Uses. Soapstone is principally used for sinks, laundry tubs, lavatories, cores for electrical heating elements, table tops, acidresisting tanks, fireplace linings, and fine pressed building and enamel brick, etc. It is valuable on account of its high electrical resistance, resistance to heat and to acids, and its slow radiation of heat.

Arkansas's soapstone has not yet been exploited, despite the fact that existence of a deposit of the material has been long known. It has been used locally for furnace linings.

Occurrence.-Massive soapstone beds underlying slabby Ordovician sandstone occur in Saline County at the Wallis' soapstone

quarry near the old Hot Springs-Little Rock road, in the northeast quarter of Section 15, Township 1 north, Range 15 west, near Cane Creek. Eight openings have been made in the deposit, which has a dip of 80 degrees and a width of approximately twenty feet. Its mode of origin is not fully understood.

The quality of the soapstone varies. A considerable portion of it appears to be of discolored and of inferior quality, while a small amount of high grade material has been taken out. The deposit undoubtedly merits thorough prospecting.

Bibliography of Soapstone

Comstock, T. B., "Gold and Silver."-Annual Report of the Arkansas Geological Survey for 2888. For soapstone see pages 30, 31, 34, 290. Out of print, but may be consulted in scientific or public libraries.

TRIPOLI

Composition. Tripoli is a form of silica which is derived from either the alteration of chert, chalcedony, or novaculite, or the leaching of highly siliceous limestone.

Uses. Tripoli is used for foundry facings, for polishing and buffing powders and pastes, and for soap powder and "sand" soap. 'It is also used as a filler for paints and for rubber, etc.

Occurrence. There are very probably many places in the novaculite district of western Arkansas, including Hot Spring, Garland, Montgomery and Polk Counties, where a good grade of tripoli formed by the alteration of novaculite can be located. A good grade of tripoli is found in a bed about ten feet in thickness on the MalvernHot Springs road about half a mile north of Butterfield. This is derived from novaculite. Other beds have been reported near Delight, Pike County, near Rogers in Benton County, (probably formed from decomposed Boone chert), and in Washington County where it is probably from the same source as the Benton County bed.

Producers. (1) Butterfield Tripoli Company, J. W. Suggs, secretary, Butterfield, Ark.; (2) Benton County Mineral Company, Rogers, Ark.

1.

2.

Production. There are no production figures available.

Bibliography of Tripoli

1892

Branner, J. C., "The Zinc and Lead Region of Northern Arkansas," Annual Report of the Arkansas Geological Survey for 1892, Vol. V. Ob tainable from the Arkansas Geological Survey, State Capitol Building. Little Rock, Ark.

1924

Butler, P. B., "Tripoli, Its Properties, Occurence, History, Preparation, and Uses," Metal Industry, January, 1924. Obtainable from the Metal Industry, New York, N. Y.