Mineral Industries and Geology of Certain Areas - Vermont Agency ...

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REPORT OF THE VERMONT STATE GEOLOGIST. 37 Geological Survey, visited the locality in 1901, and his report is published in Mineral Resources of the United States. From this report the following is taken: Just to the south of the excavation made by the National Asbestos Company an important fault is visible, which strikes into the mountain in a direction 15 ° west of north, according to magnetic compass, but since local attraction sometimes appears in this region, the observation may not be exact. At all events, the fault brings the hornblendic or chloritic schist abruptly against the serpentine, and cuts off the latter from extending farther to the west. Several feet of fault breccia mark the location of the fault. The serpentine belt appears to be a broad one, but its approximate width can not he readily stated, because it is concealed by forests and because the writer's observations were of necessity made without a map. It is evident that the location of the New England and the National companies is on the northern edge of the serpentine, while the prospects of Mr. Tucker are on the eastern edge, and much lower down. The New England and National exposures are fairly near to the outcrops of the hornblende schist forming the mountain on the north. "In all the exposures where the asbestos appears the serpentine forms precipitous cliffs and the excavations have been made in the face of these escarpments. For a long time, therefore, the rock can be blown out from open cuts which will be above the general surface of theground. In the openings made by Mr. Tucker near Tucker's Mill the conditions are very similar. A hillock or shoulder of serpentine projects from the mountain side, and is bounded by gulches on the west, south and east. The openings near the town of Lowell are likewise situated in a ridge of serpentine, and have been driven in on both sides and from the northern end. The character of the asbestos.—The asbestos occurs in two distinct and contrasted varieties. In one case it forms veins which ramify in every direction through the serpentine. The asbestos fibers are perpendicular or at a high angle to the walls,
38 REPORT OF THE VERMONT STATE GEOLOGIST. and vary from a maximum length, as at present exposed, of three-fourths of an inch down to not more than one-sixteenth. of an inch. The variety is similar in all respects to the Canadian product, but it is met only in the prospects owned by Mr. Tucker at Tucker's Mill and near Lowell. The second variety of asbestos is what, for lack of a better name, I will call ' slipfiber,' because it occurs upon the slickensided surfaces that are common to this exposure of serpentine just as to all others the world over. These fibers form layers of varying thickness, seldom more than a quarter of an inch, but as they run parallel to the slickensided surfaces they may themselves be of various lengths, from a fraction of an inch tip to 3 or 4 inches. The fiber is coarser than that of the veins, and will not furnish sc good a grade. At the same time it occurs in larger quantity. This is the variety of fiber which will be produced by the New England and the National companies. It also appears in a minor degree in the other openings. There is little doubt that the region will become commerciallv productive, and that very considerable amounts of asbestos will he contributed by it to the markets. It is possible that in time larger veins may be discovered which will give the first grade, but at present all estimations of value should be based upon a product of second and third grade. Under present conditions there seems to be an excellent opportunity for these to prove remunerative. The serpentine belts, as shown by the geological survey of Vermont, run for great distances to the north, and while it is impossible at this time to report other definite discoveries, the area within which the geological formations are favorable for the occurrence of asbestos appears to be considerable. At the same time, the existence of serpentine does not necessarily imply the presence of asbestos. Even in the belt on Belvidere Mountain the fiber is sharply limited to restricted localities. Although the serpentine has been somewhat carefully searched already, and was in large part traversed by the writer, in company with Mr. Tucker, vet no other exposures were observed which appeared to be anything ME REPORT OF THE VERMONT STATE GEOLOGIsT. 39 like as favorable as the ones which have been opened. In many ledges no fiber appeared at all." While the existence of asbestos on and near Belvidere Mountain has long been known, it was not until in 1899, when Mr. Melvin E. Tucker, who has extensive lumber interest in the region, gave his attention to the development of the mineral, that the extent and value of the asbestos bearing serpentine was realized. I have carefully examined the serpentine shoulder of the mountain, and I think that the asbestos is more widely distributed than would be indicated by Professor Kemp's last paragraph. In a report of one of the meetings of the New York Academy 21, 1901,* of Sciences, October Professor Kemp is quoted as saying: " The serpentine seems to have been derived from enstatite, cliallage and probably olivine, since unaltered nuclei of these minerals are found in it. * * * It is difficult with the data in hand, * * to trace the geological history of the serpentine, but it must have been originally either an igneous pyroxenite or peridotite or else a richly magnesian siliceous limestone. There are such slight traces of ca l cium_bearing minerals, however, that the former supposition has greater weight. The hornblende-Schist consists in largest part of commOil green hornblende, but one may also observe epidote, zoisite and some minor accessories." The South Duxhury locality is also in many respects very promising. The asbestos here is of the same chrysotile variety as that at Belvidere Mountain. So far as I could judge from surface indications and an examination of the few places where small blasts have been made, the quality is quite as good, and I should think the chance of obtaining long fiber better. We find here a serpentine ledge which extends from South Duxbury southward over the line into Moretown. The general trend of the ridge is nearly north and south, being a little east of south at the south end. I should estimate the length of the ridge at about two hundred rodis, and its width at an averae Science, vol. XIV, p. 773.
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