INTRODUCTION.

Near the south end of the Deadwood claim a shaft has been sunk and work done principally by lessees. It is called the Deadwood No. 2 mine, and is estimated to have produced $150,000. The shaft is 850 feet deep and has nine levels which represent about 4,000 feet of drifting and crosscutting. The elevation of the collar is 10,410 feet.

GEOLOGICAL FEATURES.

The shaft and workings are in latite-phonolite. Levels 2 and 9 appear to enter breccia 140 feet west of the shaft, but this point could not be definitely determined. A 3-foot vertical phonolite dike striking about north and south is exposed on level 2 about 150 feet west of the shaft. The important geological feature of the mine is a basaltic dike cut by the shaft at level 1, having a general course about N. 20° W. and dipping on an average 80° W. The dip varies considerably, however, as does also the strike. The dike is irregular in width, ranging from 1 to 5 feet, but becomes more uniform with depth.

On level 1 it appears to branch south of the shaft. The drift leaves the dike and soon cuts another approximately parallel dike. On level 2 a similar occurrence is met with just north of the shaft. Twenty feet north of the shaft on level 1 the dike is faulted, the north part being thrown 1 foot to the west. A narrow seam with a strike parallel to the dike, but which dips every steeply toward the west, branches off from the dike just below level 1. On level 6 this seam, which is still at the shaft, carries 6 inches of decomposed basalt. It is cut again on the lower levels, where the dip becomes slightly less and the width of basalt increases to 15 inches on level 9. The main basalt dike shows a corresponding loss in width as the other widens.

CHARACTER AND OCCURRENCE OF THE ORE.

On the first level a northwesterly vein dipping about 75° SW. is reached by a northeast crosscut 100 feet from the shaft. It consists of a partially oxidized, shattered, and sheeted zone in latite-phonolite. A small bunch of ore was encountered just above the level. A stope 3 feet wide, 25 feet long, and 15 feet high furnished a carload of $15 screenings. What is probably the same vein was explored for a short distance on the second level, but showed no ore.

The principal amount of ore came from the basalt dike. This is everywhere very soft and at the sides lies a decomposed, more or less clay-like gouge, which is in places oxidized, and which varies in width from a very narrow seam to several inches. The values occur in this partly as tellurides and partly as rusty gold. Where the values are exceptionally high the near-by basalt and country rock also may constitute ore. But since in general the dike was worthless, it was carefully shot down and then the soft selvage was picked down and caught on sheets. The process is called stripping, and requires no sorting. The value of the material so obtained varied considerably, but was always good, the range being $80 to $3,000 per ton.

ORE SHOOTS.

Beginning at the surface about 50 feet north of the shaft, on the basalt dike, is an ore shoot 130 feet long, which pitches steeply to the south. At level 1 it has been stoped 120 feet along the dike, the value of the ore shipped being about $80. On level 2 the shoot is 60 feet long and nearly vertical, the pay streak at the side of the dike being 1 to 8 inches wide. A small lot of gold-bearing rock too low in grade to be profitably worked, was taken out 40 feet south of the shaft on this level. On level 3 the shoot has been stoped for 50 feet. Between this and the next level the dike flattens considerably, and the ore shoot turns from nearly vertical to a much flatter pitch to the south, narrowing up and finally pinching out just before reaching the fourth or 400-foot level. Below level 4 the dike steepens again, but no ore was found between the fourth and fifth (470-foot) levels. Between the 470- and 550-foot levels occurred the richest ore in the mine.

The pay streak was wider and the values better than elsewhere. The ore shipped brought returns of $300 to $700 per ton. The stope here was almost 300 feet long. For 120 feet in the middle the main values were on the hanging wall, while at each end of the stope they were on the foot wall. Where the pay streak crossed the dike at the south a triangular body of very rich ore was formed, the screenings from which shipped at $1.37 per pound. At the north end, however, only a narrow seam crossed from the hanging to the foot wall. Below level 6 the ore was of good grade, but was confined to a narrow strip on the hanging wall, directly under that which occurred on the hanging wall above. Between levels 7 and 8, 650 and 750 feet, respectively, from the surface, the pay streak was exceedingly narrow. A stope 120 feet long is continuous with that on the two levels above, and a stope 40 feet long was made about 50 feet to the north of the main ore. Stoping is in progress upward from level 9 in a corresponding position to the main stopes above. The values are contained in a soft greenish-black material one-half inch to 3 inches wide, mainly on the foot wall. Its value is about $275 per ton.

To summarize, there are two principal ore shoots on the basalt dike. One begins at the surface 130 feet, pitches steeply to the south, and gradually shortens till it pinches out about 385 feet below the surface. This shoot is fairly regular in form and the values are pretty evenly distributed through it. The second shoot, which is directly below the first, begins at the 470-foot level and has been proved to the 850-foot level. It is irregular in form and the values which it carries vary greatly in different parts.