SPARRY LIMESTONE. 399 



"To recognize the characters of this rock, is a matter not at all difficult in the field : its 

 curiously checkered surface, formed by a milk-white calcareous spar branching out upon 

 a gray ground, will, it is conceived, be sufficient to create in the mind an image of the 

 rock, and to impress upon it one of its most characteristic features. This rock is suffi- 

 ciently pure to be used for quicklime ; and accordingly, along the belt of country which it 

 traverses, it is often burned for that -purpose. When it is sound, and can be obtained in 

 suitable masses free from flaws, it would form a handsome veined and clouded marble. 



"A subject worthy of attention, is the period of the formation of the veins of calcareous 

 spar. From observations upon other rocks, which contain fossils, which of course are free 

 from calcareous veins at the time of their inclosure in the materials of the rock, it seems 

 to be established that those veins were formed subsequent to the consolidation of the rock ; 

 for it is not an uncommon circumstance to discover a shell traversed by a vein of spar. 

 The most rational explanation appears to be, that the rock in drying, or in the process of 

 consolidation, cracked in every direction ; and into the fissures thus formed, pure calcare- 

 ous matter was infiltrated in sufficient abundance to fill the open space thus produced in 

 drying." 



The term sparry limestone should not be limited to the Eolian limestones ; for we 

 find it in other groups, as for instance in the Hudson River group, as we have already 

 shown. It denotes simply a lithological variety of several rocks. 



A brecciated limestone is found at several localities in this formation. At South Wal- 

 lingford (Nos. ^^, 3^5, in the Cabinet), west of Gen. Hall's marble quarry, it is of a 

 bluish color exceedingly like the Plymouth brecciated marble. In Rutland immediately 

 overlying the western range of the quartz rock, there is a limestone apparently brecciated, 

 and remotely resembling the previous specimen. Both are from the western limits of the 

 same group of limestone. The latter as it lay in rough blocks upon the side of the road 

 appeared like certain highly fossiliferous rocks that we had seen upon the shores of Lake 

 Champlain. We are not sure but the convoluted ridges and depressions of this rock, 

 becoming more prominent by exposure, may be fucoids. Geodic masses an inch or two 

 in diameter are frequent in it also, producing many of the ridges. Micaceous films 

 sometimes surround the geodic masses. The general color is a dark bluish gray. The 

 fragments of the limestone imbedded are of a dark brown color. The bed is from forty to 

 fifty feet thick in the northeast part of Rutland, and probably is at least a mile long. It 

 is on the east road from Rutland to Sutherland's Falls. 



In the east part of the limestone, near its northern extremity, a tough, white, brecciated 

 limestone occurs, as at Painesville. 



Micaceous limestone usually occurs only at the junction of the limestone and mica 

 schist, and is not very abundant. It frequently resembles gneiss. The best locality of it 

 is in North Adams, Mass., at the excavation for the Hoosac Tunnel. The same variety 

 in Vermont is less marked. 



The coloring matters of the limestones are usually derived from minute particles of slaty 

 matter disseminated through them. Hence they never fade or disappear, or change their 

 position in the slabs after they have been quarried. The occasional stains which appear 

 may be produced by a small portion of pyrites, affording a dirty brownish hue. Most of 

 the iron rust stain upon the blocks of marble at the mills is temporarily produced by 

 particles of iron worn from the saws. 



