REPORT OF THE DIRECTOR AND STATE GEOLOGIST 1900 r99 



tact between gneiss and limestone it plunges 15 feet in a water- 

 fall. The limestone from this point has been largely removed by 

 the cutting of the stream below the waterfall, and the exposed 

 section exhibits the lines of dark silicates drawn out in every 

 direction from n. 40 w. to n. 15 e. It is not possible to prove the 

 existence of a fault, and the relations between limestone and 

 gneiss at this point are therefore not those which obtain between 

 t)eds in a sedimentary series. 



The gneiss of Minerva township is a heavily bedded rock of a 

 light gray or brownish gray color. It is of medium grain and 

 varies but little from place to place. The combination of quartz 

 and microcline with more or less plagioclase is characteristic of 

 it. The feldspar and quartz occur as rounded or subangular 

 grains often with layers formed of larger masses of quartz drawn 

 out in lenses. The single grains of quartz are not much broken 

 up by cracks and do not appear to have been greatly crushed 

 by metamorphic processes. Recementing of the grains by second- 

 ary quartz or feldspar was not observed. The quartz is char- 

 acterized by minute inclusions of rutile, and by having many of its 

 cracks filled with microscopic dendritic growths of Mn02. The 

 microcline exhibits the usual lattice structure. The plagioclase 

 shows very fine twinning lamellae, and broad ones, alternating. 

 Granophyric growths with orthoclase may be observed. The 

 plagioclase usually occurs as an accessory to the microcline but 

 it may be almost the only feldspar present. On the western slope 

 of Snyder hill the gneiss is locally almost pure feldspar. Biotite 

 is the usual dark silicate. It often appears altered to chlorite. 

 Garnet is common. Apatite occurs sparingly, but the crystals 

 are of unusual perfection with the basal cleavage but little 

 developed. Magnetite is commonly met, and epidote, in bottle 

 green crystals well terminated at one end, has been observed. 



The gneiss is almost always found in Minerva township with a 

 strike from n. 25 w. to n. 50 w. The dip is usually to the north- 

 east and runs from 20° to 40°. This general concordance in strike 

 and dip between the heavy bedded gneiss and the limestone was 

 not suspected till over a hundred localities had been visited, but 



