112 GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



In a considerable number of thin sections the enstatite structure was 

 found everywhere strongly marked by broad, distant, granular bands of 

 black ore, with very numerous straight, narrow lines made up of rods and 

 grains of the same black ore and running at right angles to the broad bands. 

 No trace of enstatite could be found unchanged, and the broad apple-green 

 plates, which are often quoted as marmolite, from these localities had passed 

 for the most part beyond the bastite stage into a network of serpentine 

 needles, in which isolated bastite plates still remain. 



Irregular grains and large patches of carbonate, much corroded and 

 polarizing with a soft amber color, with faint irised border, occur every- 

 where; also miscroscopic veins of satin spar, sometimes insinuated in large 

 number between successive plates of the bastite. 



No trace of olivine structure could be discovered in any of the 

 slides from this locality ; and in the localities described later, where the rock 

 is less changed, it could be seen that all of the rock exposed was made up 

 of large enstatite cr3^stals so closely apposed that there could have been at 

 best only a trace of olivine present; and on the broad cleavage surfaces of 

 the enstatite no trace of included olivine grains could be seen. The structure 

 in the completed serpentine was everywhere the rectangular network, as 

 characteristic of the enstatite-serpentine as the olivine network is of the 

 latter mineral. It is beautifully illustrated by Dr. Wadsworth in pi. 7, fig. 

 2, of his Lithological Studies,^ from a specimen obtained "four miles 

 from Westfield Center, Westfield, Massachusetts." This must have come 

 from the Atwater ledge, which is just 4 miles west of Westfield -vdllage, 

 but lies across the line in Russell. As the rock from which the serpentine 

 was derived was a nearly or quite pure enstatite rock. Dr. Wadsworth's 

 assignment of it to the peridotites can not be accepted. 



16. ^^ LiffJif-f/recn, compact serpentine. — Russell." XIII, No. 25, Massa- 

 chusetts Survey Collection. This is a superficial layer a few millimeters 

 in thickness, which also runs in veins into the black serpentine, and is super- 

 ficially covered by a rusty white layer. It is probably from the surface of 

 the above bed. It presents under the mici-oscope a tremolitic structure 

 throughout — radiated, fibrous, a late stage of the change into serpentine. 



17. '^Serpentine (bowlder). — Russell." XIII, No. 50, Massachusetts 

 Survey Collection. This is certainly an erratic derived from the great bed 



' Mem. Mus. Comp. Zool. Harvard Coll., Vol. XI, pt. 1, 1884. 



