36 THE STRATIFIED ROCKS OF ESSEX COUNTY. 



otite, some muscovite and an abundance of magnetite in 

 the planes of the schistosity of the shale, fine inclusions of 

 micro-zircons are seen in the kaolinized feldspars. Some of 

 the dark opaque patches resemble lignite and it is not im- 

 possible that this shale is carboniferous, although it re- 

 quires more field work and lithological study to prove it. 

 In the line of the strike to the northeast, across the Ips- 

 wich river in Topsfield, on the land of Mr. Peterson, two 

 hundred yards northwest of the old Endicott copper mine, 

 this shale, which is here a dull red color, protrudes in 

 several places. It is interstratified with a ferruginous 

 sandstone ; the strike remains constant, northeast to south- 

 west with the dip 50 west. The microscopic structure of 

 thin sections from the outcrop near the roadside is as fol- 

 lows : section cut across the bedding, ground-mass of earthy 

 kaolin much discolored with a ferruginous iron oxide, mag- 

 netic titanic iron, some leucoxene, original quartz grains 

 showing secondary enlargements, incipient cracks and bro- 

 ken grains and also fluid inclusions, some feldspars much 

 decomposed, muscovite scales, green chlorite, apatite, nu- 

 merous microliths and zircons, a few grains of zoisite and 

 epidote. A strongly developed shearing to the north ac- 

 counts for the crushed and broken appearance of the quartz 

 and feldspar grains. Section across the bedding from a 

 specimen of the outcrop in the field on the opposite side 

 of the road, near the dwelling house of Mr. Peterson : 

 ground-mass composed of earthy kaolin and fibrous chlorite, 

 magnetite, titaniferous iron surrounded by leucoxene, 

 micro-zircons, apatite, numerous microliths so small that 

 they cannot be determined with the highest power of 

 the miscroscope, quartz grains with numerous fluid inclu- 

 sions, muscovite and a few grains of zoisite' are arranged 

 parallel to the bedding. Ferruginous sandstone from 

 Peterson's land, Topsfield (Sec. 81) : ground-mass of 



