690 



GEOLOGY AND TOPOGRAPHY OP THE LEAD REGION. 



Vein, is a term little used; it denotes the filling of ore and accom- 

 panying minerals, or either, found in a crevice. 



Lode or Lead^ are words usually substituted for vein ; they are, 

 however, generally applied to ore deposits found either in crevices or 

 openings. 



S wither, a metalliferous crevice, making an angle with the prin- 

 cipal vein or lode, sometimes called a quartering crevice. 



8 o'clock, 10 o'cloclf, etc, ranges whose course bears toward the 

 sun at those hours of the day. 



Openings. They are of two kinds, vertical and horizontal. 1. 

 Yertical openings are known as crevice openings, which are mere en- 

 largements of the crevice in certain parts, these being sometimes co- 

 extensive with the vein in length, and sometimes mere local enlarge- 

 ments. There are in the same crevice frequently several openings, 

 situated one above the other, separated by beds of unproductive rock. 

 Crevices varj' in width from one to several feet; when very wide and 

 high, they are sometimes called tumbling openings. 2. Horizontal 



openings are large 

 irregular spaces 

 between the strata 

 which contain the 

 lode. Such open- 

 ings are usually 

 from one to four 



Fig. 1L 





=5Es|^ feet high, and are 



^2 frequently super- 

 T^r^ g imposed upon one- 

 r^ another, separated 

 ^^"^ by an unproduc- 

 tive rock called a 

 The "cap" 



Sbctiok of Openings (ideal). 

 A, Crevice; B, Crevice openiug; C, Flat opening; D D, Plat openings "cap, 

 connected by B E, Pitcliing slieets ; P, Pocltet with ore. „ 



01 one opening be- 

 ing frequently the "floor " of the one above it. 



Pockets are small irregular cavities in the strata in whicli ore is 

 frequently obtained. 



Cliimneys are irregularly shaped vertical holes found in crevices; 

 sometimes connecting openings, and at othei-s extending from the 

 surface of the ground to some particular stratum of rock. 



Sheet. This is a term usually employed to designate a solid body 

 of ore exclusive of other minerals which may fill a crevice or open- 

 ing. A sheet is said to "pitch" when it inclines considerably from 

 the perpendicular. 



