THE POSTEEIOR SQEET, 471 



fraction of an inch thick to broad hiyers, were washed onto the trap and 

 sank into its mass, so that the upper 3 or 4 feet of the trap is kneaded full 

 of the dai-k, compact shales, which have at times glazed and wrinkled sur- 

 faces as in the ordinary shale, especially at the south end of the quarry, 

 and for 3 or 4 feet the trap and shale are kneaded together; shreds and 

 broad plates of the dark-gray, thin-laminated shale are twisted and plicated 

 in the black trap. 



In sections thin tortuous layers of the shale can be seen in the traj), at 

 times directly inclosed by the trap, at times a part or the whole of a tilm 

 resting in the bottom of a steam hole, as if the moisture of the nmd had 

 furnished the steam to form a cavity too large for the mud to fill. I'he 

 sandstone above wraps over the very irregular surface of the trap, which 

 rises and falls 20 feet within the limits of the quarry and dips 17'^ E. It 

 fits itself also around smaller irregularities and separate blocks of the trap, 

 and for several inches it is very ferruginous and contains small, flat con- 

 cretionary grains like the Clinton iron ore. The trap is fine-amygdaloidal 

 for 12 feet down from the suriace. 



A north-south fault appears in the quarry with an ujjthrow of 4 feet 

 on the east, dip 8° E., and many strong slickensides ajjpear parallel to this 

 surface. In pockets along this zone of crushing occur datolite crystals 

 of richer color and more brilliant luster than any found elsewhere in the 

 State. They are described in the Mineralogical Appendix, Chapter XXII. 



There were opened in 1892, near the north end of the quarry and a few 

 feet back from the railroad and 10 feet above its level, a series of pockets 

 in the solid amygdaloidal trap, a foot or more below its surface, which 

 were filled with the finest broad lamellar anhydrite,^ with some coarsely 

 granular calcite near the borders. These pockets were small and 

 UTegular, never more than 3 inches thick and 4 inches long, iluch 

 very coarsely cleavable calcite appears also in fissures in the sandstone 

 for a little distance above the trap, inclosing cavities from which gyp- 

 sum has disappeared, and within the same limits broad fissures in the 

 sandstone have their walls coated with thick layers of specular iron in 

 drusy surfaces of fine plates, and much of the sandstone is cemented by 

 shining scales of hematite. The sandstone over the trap has alternating- 



'This is a most unusual occurrence of the mineral. It occurs rarely in the Monte Somma 

 bombs. R. Brauns, Neues Jahrbuch fiir Min., 1894, p. 257. Sre Mineralogical lexicon : Bull. 126. 



