imiLDING AND ORNAMENTAL STONES. 43.1 



nearly bhick, in color. It is used to some extent for building material 

 and also in cemetery work. The Tenant's Harbor (Saint George, Knox 

 County) stone closely resembles that of Addison, and is used for sim- 

 ilar purposes. These are all most excellent stones, and it is a matter 

 for congratulation that they are being so extensively introduced, and, 

 to some extent, replacing the marbles in monumental work. The cost 

 of working is, owing to their compact structure, somewhat greater than 

 that of granite, but the results fully justify the increased outlay. All 

 the above, it should be noted, are known commercially as " black gran- 

 ite."* 



Massachusetts. — Diabase is quarried for foundation walls, general con- 

 structive purposes, and monumental work at Medford and Somerville 

 iu this State. Samples received from these localities are, however, 

 coarser, lighter in color, and much inferior in point of beauty to those 

 just described. 



Nciv Jersey. — The extensive outcrops of diabase, or " trap-rock," 

 known as the Palisades of the Hudson Eiver in northeastern New Jersey 

 furnish an inexhaustible su^^ply of this material, and which is at present 

 quite extensively quarried about Guttenberg, Weehawken, West New 

 York, and southward along the Palisades a.s far as Montgomery ave- 

 nue in Jersey City.t The rock is used chiefly' for paving, and the quar- 

 ries are small affairs worked by gangs of from two to five men. Two 

 sizes of blocks are prepared. The larger, which are known as speciQca- 

 tion blocks, are 4 by 8 or 10 inches on the head and 7 to 8 inches deep. 

 The second size, which are called square blocks, are 5 to 6 inches square 

 and G or 7 inches deep. The specification blocks bring about $30 per 

 thousand in the market, and the square only about $20 per thousand. 

 It is estimated that some 4,000,000 of the specification and 1,000,000 of 

 the square blocks were quarried in 1887, valued at $140,000. 



There are three jirincipal grades of the rock quarried. A fine-grained 

 variety at Mount Pleasant, a rocky hill north of the Pennsylvania 



Railroad ; a light-gray variety at Pergen Cut, south of the railroad ; 



■ — — ■ — — — ■ — m 



* It .should bo roiiiarketl that all of these diabases differ radically in structure and 

 composition from any othera hero mentioned, and deserve a more thorough and 

 careful study than they liavo yet received. All contain a rhombic pyroxene pleo- 

 chroic iu retl, green, and brown colors, and which is evidently hypcrsthene, while 

 certain sections of the Addison rock show a pyroxenic constituent carrying an abun- 

 dance of the rhombic inclosures so characteristic of entstatito. Both the Addison 

 and Vinalhaven rocks were in the collection and marked as diabase on my assuming 

 charge, and as such I considcu'ed them in my paper on the Maine building stones 

 (Proc. Nat. Mus., Vol. vi, 188o). The Tenant's Harbor rock is presumably the on(^ 

 described as olivine diabase by Watlsworth and Dickerson (Proc. Bos. Soc. Nat. llist., 

 Mar., 1884, p. 28). 



tTho Hudson Kiver Palisade rock is called greenstone by Mahan (Civil Engineer- 

 ing, p. 3), who states that it is composed of hornbhnide and common and compact 

 feldspar. This is obviously an error. The rock contains neither hornbleiule nor 

 ''common" (orthoclaso) feldspar, but is wholly coiuposod of augito and iilagioelaso 

 feldspar willi a few minute accessories, :i,s maguclilc an<l apatite. 



