THE COLES BROOK LIMESTONE. 



27 



the former often associated witli the ch(iiidr()(litt', tlie latter always iu small 

 complex crystals. 



THE COLES BROOK LIMESTONE. 



The limestones of this locality are first noted by President Hitchcock 

 in his Final Report^ as occurring in the west part of iMiddlefield on Pon- 

 toosuc turnpike and on the railroad at the mouth of Coles Brook and 1 mile 

 east. Both beds are said to extend south into Becket, one, the easterly (?), 

 appearing in the southeastern part of the town, on the "Billv Messinger" 

 farm; also 2 miles farther south, on the old Becket turnpike. It is a more 

 or less crystalline, white, impure magnesian limestone. A delicate variety 

 of serpentine is mixed with the limestone, forming a beautiful verd antique, 

 and in the south of Becket tremolite, talc, and titanite occur in it. 



The followina: analyses are g'iven:'^ 



[No 1, Coles Brook; Uo 



Analysen of Coles BrooJc limestone. 



, 1 mile east of Coles Brook (o) ; No. 3, Becket, southeastern ])art ; No. 4. Blanilford. J 



CaCOa- 



MgCOa 



Fe^O;, . 

 SiO..... 



Sp. gr. 



56.25 



3L56 



L12 



1L07 



100.00 

 2.78 



88.02 

 9.91 

 0.15 

 L92 



100. 00 

 2.71 



58.31 

 28.61 

 1.24 

 11.84 



100.00 

 2.82 



5L66 

 39.48 

 0.91 

 7.95 



100. 00 

 2.77 



a This locality, 1 mile east of Coles Brook, can not be located. The analysis contains so little magnesium and 

 silicon that I suppose the specimen came from a bowlder of the Stockbridge marble. 



I have added the analysis of a limestone from Blandford from the same 

 table, which proves to be a bowlder, doubtless from the Becket locality, 

 and, like it, contains tremolite and talc. These large bowlders occur abun- 

 dantly, and the one which is noted in the 1841 report as a ledge of lime- 

 stone, in the northwest portion of the town of Blandford, was found to be 

 a bowlder by Mr. S. A. Bartholomew, who used it and many others iu his 

 limekiln and traced them northwest to the outcrops in Becket. The micro- 

 scopic description of the Hinsdale station limestones given above will apply 

 wholly to these, and the change of chondrodite into the serpentine may 

 be followed better here. The former rock is, however, coarser, and the 



' Geol. Mass., 1841, pp. 81, 85, and 567. 



2 Ibid., p. 80. 



