LONG AND DBRRY MINES. 5(.)U 



These chambers are irregularly distributed through the upper part of the 

 Blue Limestone, and, as the latter has been more or less eroded, some of 

 them formed actual outcrops of ore on the surface, and were thus easily dis- 

 covered in the commencement. The mine is opened by both tunnels and 

 shafts, but the ore is mainly extracted through the former. The Faint Hope 

 (M-4) tunnel runs 180 feet through limestone and vein material and .'i(30 feet 

 in White Porphyry, to the bottom of the Porphyry (E -37) shaft. The latter 

 passed through 98 feet of porphyry and was sunk 4(j feet in vein material 

 containing nodules of chert and low-grade ore. The Long and Derry (E - 32) 

 tunnel runs in a southerl}' direction from the hillside overlooking Iowa gulch, 

 starting in White Porph3-ry and being expected to reach the contact at 500 

 feet. In the Dana (M-3) shaft were found many chert nodules in the por- 

 phyry, which carried casts of fossils, principally Pleurophorus and Spirifera. 

 Such included chert nodules are frequently found not far from the contact 

 plane and were evidently caught ujj in the mass of the porphyry as it forced 

 its way along between the strata. The whole body of the limestone on 

 Long and Derry Hill seems to be more or less impregnated with oxides of 

 iron and manganese and with silicious material, as shown by the black 

 outcrop at the Belcher (M-5) mine, near the base of the formation. In 

 this outcrop the replacement evidently proceeded from above, as the ore 

 wedges out at the bottom. The apparently broken character of the forma- 

 tion in the vicinity of the ore deposits may be due in a measure to its 

 proximity to the surface and want of a protecting covering of Wash. In 

 one portion of the mine was a large accumulation of angular blocks of 

 porph5ay in the limestone, which had probably fallen from above into a 

 cave that had been dissolved out by surface waters. 



The ore is carbonate of lead and chloride of silver near the surface 

 and galena in depth, the latter, as usual, being generally richer in silver 

 than the carbonate. Only small specks of pyrite have been found in it. 

 Tlie dike of Gray Porphyry, which crosses the hill in front of the Faint 

 Hope tiumel, may be supposed to have been an important factor in the 

 concenti-ation of ore here by causing a stagnation in the mineral-bearing 

 currents. 



