The Slate Industry.

Clay slate consists of siliceous clay which has been hardened and otherwise changed by metamorphosing influences, such as heat, pressure, and in some cases oxidation.

Quite a variety of minerals, generally in an exceedingly fine state of division, have been found in varying proportions throughout the kaolin mass which constitutes the great bulk of the rock. Among such minerals may be mentioned quartz, feldspar, mica, tourmaline, organic material, and hydrated oxide of iron. Carbonaceous matter accounts for the black color of slate from quarries in Maine and Pennsylvania. In the red, purple, and green slates of Vermont and New York, carbonaceous materials is wanting; the process of oxidation which converted compounds of iron into the ferric condition, thus giving the various shades of red and purple, may also have destroyed the carbonaceous material characteristic of black slate.

Uses to Which Slate is Put.

The property of slate which renders it useful as a roofing material is its cleavage, in virtue of which it may be readily split into thin sheets of suitable area. The great bulk of all the slate quarries in the United States goes for roofing, but the number of other uses to which slate is put is already large and is continually increasing. Such uses are the following:

Slate is used locally in a comparatively rough state for sidewalks, curbstones, hitching posts, underpinning, cellar walls, and door steps. As a manufactured article, after going through the mill, it is offered for the following purposes: Billiard-table beds, mantels, fireboards, register frames, radiator tops, steps and risers, platforms, tiles, wainscoting, moldings, thresholds, window sills, lintels, brackets, laundry tubs, washbowl tops, cisterns, sinks, urinals, refrigerators, blackboards, mangers, curriers. slabs, imposing stones, grave boxes, grave covers, headstones, grave markers, vault doors, water tables, belting courses, counter tops, brewers. vats, greenhouse shelves, chimney tops, switch boards, and panels for electric work. In the marbelizing process it is susceptible of considerable ornamentation, which makes it more desirable still for many of the above uses and also extends the list of its uses as follows: Table tops, stand tops, card receivers, soda-water fountains, checkerboards, door plates, signs, and paper weights.

Methods of Quarrying Slate.

Slate quarrying having been for hundreds of years an exceedingly important industry in Wales, it naturally happens that the industry in this country is largely carried on under the direction and superintendence of Welsh quarrymen who have learned the art by years of experience in their native land. Owing to the peculiarities of the slate itself, methods of quarrying applicable to other kinds of stone are not suitable to the production of slate. A successful slate quarryman has almost invariably learned his art by years of experience under competent and skilled supervision in quarries operated upon a liberal scale. While in this work general principles are recognized and applied, no rule-of-thumb methods of application will suffice, but the operator must be in possession of such trained judgment as will enable him to meet continually changing conditions both in the nature of the slate and in its environment. What might have been otherwise a fine and profitable quarry may readily be spoiled by the exercise of poor judgment in the initial steps of opening the quarry. A large amount of debris must be disposed of in connection with slate quarrying and the proper disposition of this, so as not to interfere with future developments, is frequently a matter involving careful consideration and good judgment. That serious mistakes may be made even by skilled workmen is testified to by the large number of abandoned quarries in Vermont and Pennsylvania which indicate unsuccessful operations.

Blasting is liberally resorted to in slate quarrying, and in this part of the art there is much room for the exercise of good judgment, so as to take advantage of the position of the rock as determined by the cleavage grain and natural joints, and to direct the blast so that just the desired effects may be produced. To an on-looker the skill of a quarryman in producing already planned for and predicted effects is sometimes quite wonderful.

Aside from this mental work and judgment involved in the successful development of a quarry, the mechanical operations are comparatively simple, and there is room for the employment of a considerable amount of unskilled labor. In some of the largest quarries of Pennsylvania Italians are freely employed in stripping and similar work. The tools used are of simple character. In the production of roofing slates the operations of manufacture, which consist in splitting and trimming to the proper thickness and size, are carried on at the edge of the quarry by men who are trained and skilled in this specialty and are known as "splitters." Their work involves a thorough knowledge of slate as to its cleavage, and in many cases the most successful workmen have followed the calling from boyhood up, having started as assistant to some one else in this work. Frequently a father brings up his sons in the same line of work, and in some cases this practice has been followed through a number of generations.

Manufacture of Milled Stock.

A long enumeration of the articles other than roofing slate into which slate is manufactured has already been given. In the mills devoted to this work there has been much opportunity for the exercise of mechanical ingenuity in inventing labor-saving devices and in adapting slate to new uses. While the Welsh enjoy quite a monopoly of the skilled work in quarrying and in making roofing slate, their particular skill is much less in demand in the mill itself, where all other articles of slate are produced. In the production of milled stock improvements have been rapidly made and American inventiveness has made itself felt. Much of the work involved in the production of milled stock consists in the making of slabs having smooth surfaces. Slate will not take a polish, but it may be made quite smooth by planing and rubbing with sand and emery. The planers are similar to those used for planing iron. At some localities in Pennsylvania the slate is so hard that it has to be cut with black diamond saws. In the manufacture of billiard table tops much care must be exercised to secure perfectly smooth and level surfaces, and for this purpose slate has no superior.

Slate is well adapted for ornamental purposes after it has gone through the process of marbleizing. Quite a variety of stones and wood are thus imitated in a very successful manner. The following is a list of different kinds of stone which are thus imitated: Gray granite, Mexican Onyx, fossil limestone, Devonshire marble, Tennessee marble, Circassian, Egyptian, and Pyrenees marble; and in fact all the better-known varieties of variegated marble; also blue agate, red granite, red serpentine, the various kinds of woods, and petrified wood of California. As the industry progresses the number of different kinds of imitation increases. The slab to me marbleized is first rubbed by hand with fine sand, using a wooden block covered with cloth. The marbleizing process is done in two ways. The marble having fine veins and lines running through it like Spanish marbles, is colored on a "float," as it is called; that is to say, a large vat of water is sprinkled with the different oil paints required. The effect desired on the stone is thus produced on the surface of the water, and is then transferred to the slab by simply immersing the slab and leaving the representation on it. The other method is by hand, brushes, sponges, and feathers being used to spear on the paint. In this process water colors are used.

At this stage the slab is baked overnight, the temperature of the oven or kiln varying from 175º F. to 225º F. After this first baking the slab is varnished and the baking is then repeated. Next it is scoured with pumice dust, varnished, and baked again. If any gilding is to be done it is done at this stage, after the slab comes out of the kiln for the third time. The next stage consists in rubbing with very fine pumice stone and a felt block, after which it is baked for the last time. Rubbing with rotten stone follows, and the final polish is put on by rubbing with the palm of the hand.

Slate Product and Its Value, by States.

The following table or production for the year 1894 shows the number of squares of roofing slate, its value, the value of milled stock, and the total value of slate for all purposes:

The following table shows the value of the production of slate, by States, during the years 1890 to 1894, inclusive:

(a) Includes Arkansas, Michigan, and Utah.

An inspection of this table shows that during the past year slate has been produced in nine States. The financial depression has had the effect of shutting down operations in a number of States in which the industry had not yet secured a firm foothold.

Slate Industry in the Various States.

California. -As is the case with other kinds of stone, quarrying of slate in this State has not enjoyed greater prosperity during the past year. The entire output comes from Eldorado County and was entirely devoted to roofing.

Georgia. -The slate industry in Georgia undoubtedly has a future, although operations have not been very extensive in the past. Demand for slate as a roofing material in the South has not been a keen one, but it is difficult to understand why it should not become so in view of the extending use of slate for roofing in other portions of the country. Although slate is known to occur at a number of localities in the South, the quarries at Rock Mart are the only ones at present equipped to supply any considerable demand.

Maine. -Slate production in Maine increased from a total valuation of $139,200 in 1893 to $146,838 in 1894. Of the total value in the latter year, $123,937 represents the value of 24,690 squares of roofing slate, while the remainder, $22,901, is the value of milled stock, the production of which is on the increase. The entire output comes from quarries in Piscataquis County.

Maryland. -The slate region of this State is a continuation of the York County slate belt. The Maryland quarries are all in the northern part of Harford County, near the State line. The quarries of these two counties constitute what is known as the Peach Bottom slate region. This region is discussed more fully in connection with Pennsylvania slate statistics. The Maryland product is almost entirely used for roofing purposes, 7,422 squares having been produced in 1893 and 39,460 in 1894. These products were valued at $37,884, and $150,568, respectively.

New Jersey. -The slate quarries of this State are an extension of the Pennsylvania slate belt, and only a little quarrying is annually done. The quarries are in Sussex and Warren counties.

New York. -The slate quarries of this State are all in Washington County, near the line separating New York and Vermont. The New York quarries produce slate of a cherry-red color, which is the only slate if its kind in the world. The price for this slate is much higher than for any other slate in the country. No red slate is quarried on the Vermont side of the line. In 1894 the product amounted to 7,955 squares, valued at $42,092. Many of the quarrymen operating in Vermont reside in New York state.

In the report for 1893 the value of the output of slate in New York was placed at too high a figure, on account of an error arising from the difficulty in identifying quarries near the State line as belonging to one State or the other. The figures for 1894 are exact, having been verified by Mr. George W. Harris, formerly a resident of Fair Haven, Vt., who is familiar with the Vermont and New York slate region.

Pennsylvania. -As is evident from the table of production, this State produces more than half of the entire slate output of the country. The product of 1894 was valued at $1,620,158. Of this amount $1,380,430 is the value of 411,550 squares of roofing slate, while the remainder is the value of milled stock.

The following description of the State quarrying regions of Pennsylvania is taken from the writer.s report in Mineral Resources for 1989-90:

• While there is a great variety in the colors of the slate product in Vermont, a similar statement does not apply to Pennsylvania, the product of which is entirely black, although a very fine distinction is locally made between black and a sort of bluish-black.

  The actively quarried slate belt of Pennsylvania really begins in Sussex County, in the northeastern part of New Jersey, where, at Lafayette and Newton, there are slate quarries in operation, and also in Warren County, at Polkville. The Pennsylvania portion of this slate belt begins at the Delaware Water Gap, in the northeastern part of Northampton County, and extends through Northampton, Lehigh, and Berks counties in a southwesterly direction. There is then a break filled up by Lebanon and Lancaster counties to the southwest, but in the southern part of York County operations in what is known as the Peach Bottom region reappear. Passing from Delaware Water Gap in a southwesterly direction, the most important producing localities are as follows: Slateford, Mount Bethel, East Bangor, Pen Argyl, Wind Gap, Belfast, Delman, Chapman Quarries, Treichlers, Danielsville, Walnutport, Slatington, Tripoli, Lynnport, Steinsville, and finally, in York County, a portion of which is known as the Peach Bottom region, which is for the most part in the northern part of Harford County, Maryland. The most important localities in York County are West Bangor and Delta, which may be regarded as the principal points for the entire Peach Bottom region. The slate of Pennsylvania is frequently divided more for commercial reasons than anything else, into the following regions: The Bangor region, the Lehigh, the Northampton Hard Vein, the Pen Argyle, and the Peach Bottom regions. The Bangor region is entirely within Northampton County, and is the most important. It includes quarries at Bangor, East Bangor, Mount Bethel, and Slateford; the Lehigh region includes Lehigh County entire, also a few quarries in Berks and Carbon counties, and also a small number of quarries in Northampton County, on the side of the Lehigh River, opposite Slatington; the Pen Argyle region embraces quarries at Pen Argyle and Wind Gap, in Northampton County. The hardness of the slate as compared with that produced in other regions of the State. It includes the following localities: Chapman Quarries, Belfast, Edelman, Seemsville, and Treichlers, all in Northampton County. The Peach Bottom region includes four quarries in York County, Pa., and five in Harford County, Md.

  One of the chief difficulties met with in quarrying the so-called "soft" slate of Pennsylvania is the occurrence of what is known as "ribbons." These ribbons are composed of foreign material and are exceedingly hard and interfere not a little with the smooth and economical quarrying of the slate. These ribbons are entirely wanting in the Peach Bottom slate, and this makes a great difference in the east of quarrying in favor of the product of the Peach Bottom region. The slate produced at Chapman Quarries and other localities quarrying the same kind of slate that is produced at this locality is so extremely hard that although it can be split with about the same readiness as the soft slate, it has to be sawed with diamond saws. This hardness is naturally an advantage to the slate, rendering it durable and nonabosorptive. For flagging purposes it is extremely well adapted, chiefly on account of its hardness. The most important product into which this hard vein slate is made is roofing slate, although it finds considerable application for billiard tables, imposing stones, blackboards, cisterns, lintels, window sills, copings, ridgepoles, stairsteps, and floor tiles. For paving purposes it has given great satisfaction.

  The largest quarry in the State, and probably in the country, is the old Bangor quarry at Bangor. The dimensions of this quarry are 1,100 feet long, 350 feet wide, with an average depth of 175 feet. Operations are conducted on a very large scale here in every respect, two locomotive engines and a large number of cars being kept during a part of the year almost constantly employed in stripping and transporting the surface material to the dump.

  Slate quarrying not only in Pennsylvania, but in all other States producing slate, is carried on almost entirely by the Welsh, in so far as skilled labor is concerned. This is of course due to the fact that operations of quarrying slate have been better studied in the enormous slate quarries of Wales than in any other part of the world, and naturally labor skilled in slate quarrying comes from that country. For ordinary labor, such as stripping, Italians supply most of the demand. A large school-slate factory is in active operation at Bangor. In this factory the operations are carried on almost entirely by machinery, which is so perfect in its working that the manual labor required in attending to it is largely monopolized by children of both sexes. Similar statements may be made of large and prosperous school-slate factories in operation in Slatington and Walnutport. In the manufacture of roofing slate, boys are quite freely employed in the work of trimming the slates after they have been split to the proper thickness and approximate size. This practice enables the Welsh to keep the skilled work largely in their own hands, as they bring up their sons to learn the business after them, beginning with the light work of trimming, and as they grow older and stronger extending their work to the heavier operations.

Vermont. -The slate output of this State comes entirely from quarries in Rutland County. The industry has suffered quite noticeably from the financial depression which has characterized the years 1893 and 1894. The total value of the output of 1893 was placed at $535,732. As explained in connection with the consideration of slate statistics in New York State, the above figures for 1893 in Vermont are somewhat low, as returns from some Vermont quarries operated by residents of New York State were erroneously returned as belonging to the latter. The value of the product in 1894 for Vermont has been very exactly ascertained to be $658,167. Of this amount, $455,860 represents the value of 214,337 squares of roofing slate, while the remainder is the value of milled stock.

The area in which slate is actually produced at present is confined to a narrow strip in Washington County, N. Y., and a somewhat wider one lying next to it in Rutland County, Vt. It extends from Castleton, Vt., on the north, to Salem, N. Y., on the south, a distance of 35 or 40 miles, and has a maximum width of 6 miles, but the average is not more than a mile and a half. Scattered over this territory there are about forty-nine quarries in Vermont, and abandoned quarries, or those which for one cause or another are at present idle, number many more. The first commercial use to be made of the slate of this region was between thirty and forty years ago, when Messrs. Alanson and Ira Allen began on a small scale the manufacture of school slates from the stone obtained at Scotch Hills, 2 miles north of the village of Fair Haven. This quarry is still in operation. The industry has now reached large proportions, the number of quarries keeping pace with the demand for the stone, and this is steadily increasing as new purposes are found for its application.

According to Mr. George W. Harris an outcropping of black slate has been observed near Benson, Rutland County. No actual developments have been made, but tested samples give promising indications both as to texture and color.

The slate differs somewhat in its physical properties, such as hardness, homogeneity, and cleavage, but the greatest variation is to be found in its color, no other place in the world showing so many colors in an area of equal size. Most of the commercial names under which the slate is sold are descriptive of the color of each kind, and are as follows: Sea green, unfading green, uniform green, bright green, red-bright red, cherry red, purple, purple variegated, variegated, and mottled.

The line dividing Vermont and New York also marks the division of two important varieties of slate. The true sea-green is found only in the former State, while the red is entirely confined to the latter, some of the quarries producing the respective kinds being, however, but a few hundred yards apart. The sea-green slate is manufactured almost entirely into roofing slates, more than three times as many squares being made from it as from all other varieties combined. It is quarried very extensively in the villages of Pawlet and Poultney. The selling price per square is lower than for any other prominent kind quarried in the region, and the greater output results both from its predominance in the localities mentioned and from the ease with which it is worked, is a pleasant grayish-green, but after being exposed to the weather it gradually fades and changes in a very unequal manner, certain sheets turning brown, others light gray, while some remain practically unchanged. A roof covered with it presents, after a year or two, a peculiar spotted appearance. It is, however, a good wearing slate, and the objection to its color is the principal one against it.

As already stated, no red slate is produced in Vermont, while the red-slate quarries of New York, just across the dividing line, are the only ones in the world producing red slate.

Virginia. -The slate industry of Virginia is developed in a satisfactory manner, and although the general business depression has affected the industry during the past two years, progress has been made both in an increase of output in 1894 as compared with 1893, and in the further perfection of mills for the manufacture of products other than roofing slate. The value of the output in 1893 was $117,347, representing the value of 27,106 squares of roofing slate and $12,500 worth of milled stock. In 1894 the total value of the output was $138,151, or which $19,300 represented the value of milled stock and the remainder that of 33,955 squares of roofing slate. Most of the product comes from Buckingham County, while the rest is quarried in Amherst and Albemarle counties.

Historical Data.

According to Mr. George W. Harris, of Fair Haven, Vt., the quarrying of slate began with the operations at the Cilgwyn quarries in Wales. From these was taken the slate used in roofing some of the oldest castles in that country. Some of these structures are said to have been in existence prior to the Norman conquest. Excavations made in one of the ancient churchyards of Wales revealed a headstone erected over the grave of Sir William Brereton, who, according to the inscription, died in the year 1651. A headstone in a graveyard at Plymouth, Mass., bears the date February 23, 1672. This slab and others were brought to this country as ballast in ships from the earliest Welch quarries.

The first use to which Vermont slate appears to have been put was the manufacture of school slates by Deacon Ranney and Colonel Allen, of Fair Haven, Vt. In 1847 the production of roofing slate began, only 200 squares being manufactured the first year. In 1855 the same locality yielded 45,000 squares of roofing slate.

 

[Top of Page]

---

Commercial use of material within this site is strictly prohibited. It is not to be captured, reworked, and placed inside another web site ©. All rights reserved. Peggy B. and George (Pat) Perazzo.