Transactions . nd cuts down through many beds of gneiss, about 60 Pinto diorite; no ore. Gray gneiss; pay ore. Black gneiss; no ore. Red gneiss; good ore. Dark-gray schist; no ore. Diagram (Plan) Showing Rocks Traversed by the Neihart Veins, and Relationof Pay-Ore to Country-Rock. (The veins are indicated by simple parallellines.) ft. thick, that d\p east. In the micaceous gneiss the vein is anearly imperceptible string of clay. In argillaceous slates itsuddenly becomes 12 to 18 in. thick, consisting of baryta,ruby-silver, large masses of antimonial silver, and argentiferousgray copper. In the
Transactions . nd cuts down through many beds of gneiss, about 60 Pinto diorite; no ore. Gray gneiss; pay ore. Black gneiss; no ore. Red gneiss; good ore. Dark-gray schist; no ore. Diagram (Plan) Showing Rocks Traversed by the Neihart Veins, and Relationof Pay-Ore to Country-Rock. (The veins are indicated by simple parallellines.) ft. thick, that d\p east. In the micaceous gneiss the vein is anearly imperceptible string of clay. In argillaceous slates itsuddenly becomes 12 to 18 in. thick, consisting of baryta,ruby-silver, large masses of antimonial silver, and argentiferousgray copper. In the hornblende-gneiss it continues, but thesilver-ores are wanting and galena is the only ore. In thefourth series, of slightly micaceous beds of gneiss, the silver-ores are as abundant as in the argillaceous slates; but theygradually disappear in depth, being replaced by selenite andgalena. It will be noted that the Neihart veins present several con-tradictions to the rule observed in the Butte district. The ores. * Geology of the Little Belt Mts., Mont., 20th Ann. Rep. U. S. Geol. , Part III., p. 419. f Geological Observer, Ed. of 1851, p. 781. in I i \. II 01 001 N i i:v RO< is OK mini B It vi:i \ 6 I 7 ur in the feldspathic rocks, carrying little ferro-magnesiauminerals. The basic amphibolite and the < 11<? i• 11«• are both bar-ren. It should be noticed also, in this connection, that the ore-depositing solutions were markedly different in the two cas<In the Neihart veins the gangue is mainly a mixture of carbon-ates of lime, ir<»n and manganese. The ores are also mark-edly different, as they consist primarily of galena with sphal< r-ite and pyrite, which is secondarily enriched in the upper partsof some veins. The solutions have been of such a characteras to react with the feldspars rather than with the ferro-mag-nesian silicates. Montana Localities.—In the silver-lead camp of Barkerin the Little Belt Mi-., near Neihart, as at the mine- a
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