12 GEOLOGICAL AND MINERALOGICAL NOTES : NO. 5. 



C. Remains of Ancient Rocks of Sedimentary Origin 

 on Cape Ann. 



(1). The principal and largest mass of this sedimen- 

 tary rock, referred to in my previous paper on the strati- 

 fied rocks of Essex County (Bull. Essex List. Vol. xxn 

 No. 1, 2 & 3, p. 45, Min. and Geol. Notes 2), is seen on 

 the shore at the westerly side of Folly Point, east of 

 Langford's Cove, in Lanesville. This outcrop varies in 

 width from 10 to 30 feet ; the strike is N. 40 E. to S.W. ; 

 the length of the outcrop, exposed between low water and 

 the covering of drift on the hillside, is about 100 yards. 



The microscopic structure is : Well rounded grains of quartz and 

 feldspar, scales of biotite, some titanite, garnets with irregular out- 

 line and some magnetite. The larger feldspars have inclusions of 

 muscovite, quartz and epidote and are surrounded by chlorite. This 

 rock is clearly a mica-schist, metamorphosed from a sandstone. 



(2). Another outcrop of this mica-schist, which is in- 

 terbedded with a granitic gneiss and chert, is seen in an 

 abandoned quarry in the Bay View region. It has the 

 same dip and strike as the outcrop at Lanesville. This 

 gneiss has the same microscopic characters as the gneiss of 

 Boxford and Andover, and farther investigation will un- 

 doubtedly show that this rock belongs to the lower Cam- 

 brian sediments, thus placing the so-called archrean- gneiss, 

 found in the large tract in the northern part of the county, 

 in this group. 



(3). On both sides of Brace's Cove, Eastern Point, 

 Gloucester, is a clearly metamorphosed sedimentary rock 

 oi irregular outline, and of considerable extent, with a strike 

 N. and S. to N.E. and dip nearly vertical, and which is 

 also seen as inclusions in the hornblende-granite of the 

 region. The microscopic structure is : Rounded and ir- 

 regular grains of quartz and feldspars cemented in a 

 groundmass of chlorite and limonite. 



