Scapolite Rock. 315 



8. SCAPOLITE ROCK. 



Associated with the limestone and mica slate of Berkshire County, 

 which extend into Canaan, Ct., extensive beds or strata occur, com- 

 posed essentially of what I suppose to be compact scapolite. I have 

 traced these strata in the town of Canaan, from six to eight miles in 

 length, and in some places from 100 to 150 rods in breadth. And I 

 have no reason to doubt but they extend much farther in length ; 

 probably into Massachusetts on the north ; and I cannot judge how 

 far south. No one, it seems to me, could regard masses of such ex- 

 tent and regularly stratified, only as a simple mineral. And if I am 

 not mistaken as to its nature, there can be no doubt it is a new rock ; 

 since in other quarters of the globe, scapolite is rare even as a min- 

 eral. I thought at first that it might be a compact variety of white 

 augite ; since this mineral does occur in connection with the same 

 limestone. But the rock fuses with intumescence and without diffi- 

 culty into a white enamel: whereas I could not melt the augite from 

 the same locality. The following are all the varieties of this rock 

 which have yet fallen under my notice. 



1. Masses exhibiting Aggregations of imperfect Prisms of Scapo- 

 lite ; too imperfect, however, to determine their form, though the foli- 

 ated structure is quite obvious. This rock is liable to partial decom- 

 position at its surface. I have found it only in bowlders. (No. 540.) 



2. Compact Gray Scapolite, exhibiting a splintery fracture. This 

 is the most common variety. It is very perfectly stratified in most 

 instances, the strata varying in width from half an inch to a foot or 

 more. Generally the surface is partially decomposed to the depth of 

 more than half an inch, resembling some varieties of anygdaloid, or 

 variolite. On account of the evenness of its stratification, it forms an 

 excellent building stone, and is employed for this purpose by the in- 

 habitants of Canaan. Not unfrequently these strata are divided by 

 seams crossing the regular planes of stratification nearly at right an- 

 gles. (No. 541.) 



3. A mixture of Scapolite and Dolomite. The proportion of the 

 two minerals is various. The limestone is most liable to decomposi- 

 tion and leaves the scapolite in irregular masses ; giving to the rock 

 a most forbidding aspect. (No. 542.) 



4. Compact Scapolite Quartz and Mica. (No. 543.) This appears 

 to be mica slate or quartz rock containing a small proportion of scap- 

 olite. 



