No. 3. — On nil Occurrence of Gold in Maine. By M. E. 

 Wadswoktii. 



The gold under consideration here is found on Seward's Island, a 

 small island in the town of Sullivan, Hancock County. The gold is 

 found in quartz veins cutting an eruptive mass of diabase. This diabase 

 forms a dike of about 40 feet in thickness, lying approximately parallel 

 to the bedding of an indurated fine-grained argillaceous mica schist ; 

 all dipping nearly S. 30'' W., 24° to 42°. The dip averages about 35°, 

 and the strike is far from being uniform. Crossing the diabase at various 

 angles, but generally from north to south, are segregated quartz veins. 

 In some places the rock is a confused reticulated mass of these veins, with 

 patches of diabase lying between them. The veins vary in width from 

 a mere seam to even a foot in breadth. Starting where only one or a 

 few of them are visible, they gradually increase in number until they 

 become quite numerous, while they will doubtless be found to fade 

 away as they began. The diabase and schists are cut by several dikes 

 of diabase running approximately at right angles to the strike of the 

 schist, or parallel to the veins. The vein stone is quartz, together 

 with some calcite, tremolite, and chlorite, and carries tetradymite and 

 gold. 



So far as examination has been made, the veins in the diabase carry 

 gold, and the decomposed diabase immediately adjacent to the quai'tz 

 veins also contains that metal to a greater or less extent. The gold 

 occurs principally in small grains in the vein in connection with the 

 tetradymite, bits of decomposed diabase, and in the cavernous portions, 

 but not in the compact quartz of the vein itself. The tetradymite is 

 in irregular grains and masses, showing a brilliant metallic lustre and a 

 well-marked basal cleavage. The locality is worked for its gold, and 

 was visited by the writer in December last. 



Cambridge, Mass., Jumiaiy, 1881. 



VOL. VII. — NO. 3. 



