ZIXC ALONE. Ill 



crop of the Buckwheat was 25 to 30 feet across, but it swelled be- 

 low to 52 feet, and in the second level, about 200 feet from the 

 surface, it was penetrated by a cross-cut 125 feet without finding 

 the wall. The character of the ore varies ; for while it is excellent 

 at the point of the cross-cut, at 125 feet nearer the intersection with 

 the front bed it becomes lean, while preserving its width lower. 

 Beyond the dike the bed is likewise broad, and is mined out for 40 

 to 50 feet across. The workings are now some distance down on 

 the pitch. The impression made by the arch of the roof and 

 by the curving beds is that this is the crest of an anticline 

 whose axis pitches north 27, and whose central portion is formed 

 by the franklinite bed being doubled up together on itself be. 

 fore the two parts diverge in depth. Its western portion probably 

 is continuous in a synclinal trough with the front bed, and its 

 eastern portion dips east at some unknown angle. If this is true, 

 it would doubtless be struck by drilling in the surface to the east- 

 ward. Mining has generally been followed along the entire out- 

 crop except at the junction of the tw r o branches. At present the 

 most active work is being done on the front bed at the Trotter 

 mine and on the rear bed of the Buckwheat, the latter being much 

 the larger. 



2.07.05. The ore consists of franklinite in black crystals^ 

 usually rounded and irregular, but at times affording quite a per- 

 fect octahedron combined with the rhombic dodecahedron and set 

 in a matrix of zincite, willemite, and calcite. The richest ore lacks 

 the calcite and consists of the other three in varying proportions. 

 This best ore is in largest amount in the Buckwheat mine, beyond 

 the trap dike which cuts it. The limestone containing the ore has 

 a notable percentage of manganese replacing the calcium, and 

 where it is exposed to the atmosphere it weathers a characteristic 

 brown. An analysis of a sample occurring with the ore at Sterling 

 Hill afforded F. C. Van Dyck : 



CaCO 3 82.23 



MnCO 3 16.57 



Fe s 8 0.50 



Si0 2 0.20 



H 2 6 1.0 



100.50 



The percentage of manganese is very high for a limestone. 



2.07.06. The Sterling Hill outcrop is less extensive. It begins 



on 



