of the Southern part of Essex County. 89 



A variety occurs at Marblehead, which very much resembles 

 the opalescent feldspar or Labradorite. It is of a grey color, and 

 occurs in veins in the trap rocks. 



Compact feldspar exists in great profusion, especially through- 

 out the region of porphyry. A variety occurs at Beverly, (Hos- 

 pital Point) in which are imbedded innumerable minute crystals 

 and grains of quartz. 



Most of the hornstone and jasper, in Lynn and Saugus, are 

 supposed to be compact feldspar, more completely fused. 



SPECIES 17, EPIDOTE. 



An exceedingly beautiful variety of epidote exists, in great 

 plenty, in veins, in the sienite and greenstone at Nahant, either 

 alone, or associated with quartz, hornblende, and other minerals. 

 It occurs also with quartz, in a vein in the sienite at New Cove, 

 Lynn. Associated with other minerals it occurs throughout the 

 coast, from Nahant to Salem, Marblehead and Beverly, forming 

 prase and other aggregates. Epidote also exists in narrow 

 veins, throughout the whole greenstone region. 



At Nahant, the epidote presents all shades of green, from a 

 greenish yellow to a blackish green, and some specimens are 

 almost black. 



SPECIES 18. PREHNITE. 



A beautiful variety of crystallized prehnite was discovered at 

 Saunders' ledge, east shore of Nahant, in Sept., 1837. It was 

 expected this would yield a supply of specimens sufficient for 

 any demands, but upon blasting, it proved that the inroads of the 

 ocean had nearly exhausted the vein. A few good specimens, 

 only, could be obtained. 



SPECIES 19. ASBESTOS. 



Fibrous ligniform and compact asbestos, occurs in veins in 

 the hornblende rocks, on the east side of Nahant, (marked on 

 Lewis' map, " the Iron Mine,") These veins are from a quar- 

 ter of an inch to three inches in diameter. 



