NATURAL HISTORY. 



47 



GRANULAR QUARTZ. 



TALCOSB SLATE. 



lets for the marble, and already largely 

 increased the marble business. AVe have 

 not room in this Appendix to go into par- 

 ticulars with regard to the yield of the 

 various quarries. There is no doubt but 

 that the marble business is destined to be 

 one of the most important resources of the 

 state. 



Granular Quartz. — This forms a nar- 

 row range, or belt, extending from the south 

 line of the state to the northern part of 

 Addison county, between the Stockbridge 

 limestone on the west, and the rocks of the 

 Green Mountains on the east. This range 

 is quite irregular, and in some places not 

 easily traced. It is mostly of a dark gray, 

 or brownish, color, and is very baiTcn in 

 minerals, containing only occasionally 

 crystals of sulphurct of iron and schorl. 



The Tacouic rocks, generally, contain 

 few interesting minerals ; and the fossils 

 which have been found in them are very 

 few and obscure. These rocks have, for 

 the most part, a steep eastern or south- 

 eastern dip. 



All the rocks, in place, iu Vermont, lying 

 to the eastward of the Champlain and Ta- 

 conic gi'oups, already mentioned, and occu- 

 pying more than three-fourths of the state, 

 have, till recently, been regarded as pri- 

 mary ; but tacts are daily coming to light 

 which render it probable that the greater 

 pai't of them belong to the paliBozoie, or 

 Silurian series, and that they have been 

 changed, and have had their fossils nearly 

 all obliterated by heat. Wc sliall not enter 

 at all into the discussion of the geological 

 age of these rocks, but confine ourselves to 

 a hasty general description of them. 



In a former work* I have regarded these 

 rocks as primary, and have described them 

 as belonging to two grand divisions, which 

 are distinguished from each other by very 

 obvious characteristics. The first of these 

 divisions, lying next eastward of the rocks 

 already described, and constituting the 

 main central body of the Green Mountains, 

 was denominated the Telcosc slate forraa- 

 tioii, or division, from the general preva- 

 lence of that rock, particularly iu the 

 northern portion of it. The other division, 

 extending eastward from this to Connecti- 

 cut river, was called the (Jalcario-mica 

 slate formation. The line between these 

 formations is, for the most part, well de- 

 fined and easily traced, from south to north, 

 through the wiiole length of tlie state. 

 From the south line of the state, in Halifax, 

 it runs in a dii'cction nearly north through 

 the towns of Nev/fane, Cavendish, Bridge- 

 water and Bethel, to Northtield, and thence 

 a little east of north through Montpelier, 



* Geography and Geology of Vermont, for Schools. 



Calais, Craftsbury and Irasburgh, to Mem- 

 phremagog lake. 



Talcose Slate Division. 



This division, which constitutes the cen- 

 tral portion of the Green Mountains, varies 

 in width from about 14 miles, in the south 

 part of the state, to 30 miles in the northern, 

 and it embraces the loftiest mountain sum- 

 mits in the state. 



The rocks of this division, though, gen- 

 erally, more or less talcose, vary considera- 

 bly, in their aspect and composition. Be- 

 ginning iu the northerly part of the state, 

 with the rocks next eastward of the Red 

 sandrock formation, we find them shaly, 

 very quartzose, and with very little talc or 

 mica in their composition. They have a 

 dip of about 40" to the east, and in some 

 places the beds, or strata, are a fine con- 

 glomerate, the rounded pebbles being, for 

 the most part, quite minute. In some 

 parts the rocks have a greenish, or chlo- 

 ritic hue, and are so thick bedded and com- 

 pact, as to make a very good building stone. 

 This is particularly the case in the towns 

 of .Tericho and Westford. 



In proceeding eastward the dip of these 

 rocks increases rapidly, till it becomes ver- 

 tical along the western foot of the Green 

 Mountains, forming a synclinal axes. The 

 line of this axis passes through the towns 

 of lierkshire, Enosburgh, Bakersfield, Cam- 

 bridge, Undeihill and Jericho. To the 

 eastward of this line the dip continues 

 nearly vertical for several miles, being 

 sometimes to the west, and, at others, to 

 the east, forming a succession of synclinal 

 and anticlinal axis. The dip then becomes 

 uniformly westward, and continues so 

 through the eastern part of the formation. 



Interstvatifled with the Talcose Slate, we 

 frequently find well characterized clay and 

 mica slates ; and in many places along the 

 slopes of the Green Mountains, the talc and 

 mica enter into the composition of the same 

 slates in such equal proportions as to make 

 it difficult to say wdiich name more proper- 

 ly belongs to it. In I'erkshire and Enos- 

 burgh there are extensive beds of well 

 characterized clay slate, jjovtions of which 

 may hereafter be found suitable for roofing. 

 A little further east, in Richford, is a nar- 

 row range of plumbaginous slate, wliich 

 has been traced southward as far as Hun- 

 tington, in the south eastern part of Chit- 

 tenden county. In Cambridge, it is found 

 sufficiently soft and black to form a tolera- 

 ble substitute for black lead. 



In many places along the western slope 

 of the Green Mountains, tlie rocks lie in 

 thick beds, or strata, each stratum splitting 

 [with nearly equal facility in all directions, 

 [and approaching to gneis in appearance 



