86 PrescoWs } Sketch of the Geology and Mineralogy 



Species 2. Carbonate of Lime, Calcareous Spar. 



Var. 1 . The crystallized and laminated, occur at Nahant, 

 and at New Cove, Lynn, some brilliant specimens have been 

 obtained ; but it generally occurs in thin veins, in the trap 

 rocks at the above, and at some other places on the sea coast. 



Var. 2. Fibrous carbonate of lime one locality of this va- 

 riety has been found on the east side of Nahant, at Saunders' 

 Ledge. 



Species 3, Magnesian Carbonate of Lime. 



Var. I . Rhomb spar occurs at the south eastern part of Na- 

 hant, in a vein in the slate. 



Var. 2. Dolomite or granular Magnesian limestone occurs, 

 associated with the argillaceous and flinty slate, on the south 

 eastern part of Nahant, between East Point and Castle Rock. 

 Species 4, Silicious Borate of Lime, (Datholite,) 



A. mineral occurs incrusting the trap rocks at Saunders' 

 Ledge, Nahant, which appears to be datholite ; but as it has not 

 been analyzed, I am unable to speak with confidence. 



GENUS IV. MAGNESIA. 

 Species 1. Carbonate of Magnesia. 



Carbonate of Magnesia occurs at Lynnfield, in veins, in the 

 rnagnesian marble of that place. 



CLASS II. 

 Species 13. Quartz. 



Var. I. Greasy quartz, occurs in veins in various parts of 

 Lynn and Nahant, but New Cove is the most celebrated locality. 



Var. 2. Bowlders of common and greasy quartz, are to be 

 found in Danvers, and the numbers increase as you approach 

 the northern limits of the town. 



Var. 3. A few pebbles of yellow quartz are to be found on 

 the borders of Nahant. 



Var. 4. Radiated and drusy quartz, occurs in veins in the 

 slate, on the south eastern part of Nahant ; also on the west 

 side of Bass Rock, 



