EVENING STAR MINE. 435 



limestone. On the limestone surface only about eight to ten feet of vein 

 material were found, which rapidly thinned out to the south and east. 1 Be- 

 tween these two shafts the rich ore body extends in a practically continuous 

 sheet, reaching its greatest thickness of about forty feet toward the middle 

 of the area. Its outlines are difficult to define, since the distinction between 

 low-grade ore and high-grade vein material may vary at different times and 

 since it could not be actually studied in every part ; but where drifts were 

 closed information had to be obtained from the miners. Its lower surface 

 is very irregular, extending down into the vein material to depths which 

 vary rapidly in a few feet ; the upper limit, however, is more regular, being 

 practically that of the contact, though every portion of this was not nec- 

 essarily rich enough to be extracted. Toward the Morning Star mine it be- 

 comes thinner, but its lateral boundaries widen. East of the Main shaft, on 

 the line of Section D, the contact is barren, but on the Morning Star line 

 the ore extends to the line of steepening dip, as it does in the workings 

 from the Morning Star Upper shaft. It is by no means certain that in this 

 region the eastern limits of the ore body have been reached, and the out- 

 lines given on the map must be considered merely tentative. The diagram 

 in Fig. 1, Plate XXII, is taken from the extremity of the incline running 

 east from the Evening Star Upper shaft and shows a fragment of porphyry 

 intruded into the body of the limestone, in this case unaltered ; such an oc- 

 currence in a region of active replacement would account for the Chinese 

 talc and clay which might be found entirely within an ore body. 



No. 5 shaft. Since the completion of field-work an exploring shaft has 

 been sunk at the outcrop, which, after passing through a considerable thick- 

 ness of vein material, is said to have found unaltered Blue Limestone. 

 From this information the structure assumed in the section has been in- 

 ferred, though, as will be shown in the discussion of the region west of the 



1 Since the completion of field-work this shaft has been sunk 100 feet deeper, cutting alternately 

 through solid limestone and replacement zones parallel with the bedding and containing iron vein 

 material. The first of these zones was 7 feet thick, occurring at 15 feet below the contact; the 

 second was 45 feet thick, containing in the middle from 5 per cent, to 20 per cent, of lead and occa- 

 sional nodules of galena. The limestone on either side of this zone was decomposed and pulverulent, 

 in the condition known to the miners as " lime-sand," but the bedding plaues were often still distinct. 

 From these developments it appears that the replacement zone on Section D should have been con- 

 tinued farther east. The shaft was not carried down to the Gray Porphyry, to determine whether 

 pay ore exists at its contact, as in the Waterloo. 



