REPORT OF THE CHIEF ASTRONOMER 157 



SESSIONAL PAPER No. 25a 



Columnar section of Beehive formation. 



Top, base of Lone Star schist formation. 



2,850 feet. — Thin-bedded, variegated (green, gray, brown, red and whitish) phyllite, 

 silicious metargillite and quartzite; weathering rusty-brown; ripple- 

 marks. 

 50 " Thin-bedded, light gray limestone, weathering gray. 

 270 " Light green-gray sericite-quartz schist. 

 1,500 ' Thin-bedded, greenish, silicious metargillite and interbedded quartzite ; 

 weathering brown; ripple-marks. 

 30 " Bed of massive white quartzite. 

 180 " Thin-bedded, light greenish-gray, silicious metargillite, weathering light 



rusty brown. 

 120 ' Massive, hard, bluish gray quartzite, weathering brown. 

 2,000 ' Thin to medium-bedded, light greenish gray quartzite, weathering rusty 

 brown, with thin, though numerous interbeds of dark greenish silicious 

 metargillite, weathering dark brown or brown-gray. Ripple-marks, 

 sun-cracks and annelide trails are plentiful. One hundred and seventy- 

 five feet from the top, a bed of magnetite mixed with lenses of magneti- 

 tiferous quartzite; this bed from two inches to eight feet thick. 



7,000 feet. 



Base, conformable top of Ripple formation. 



Ripple-and rill-marks, sun-cracks, and, less often, annelide trails and bor- 

 ings are common at many horizons. 



The bed of magnetite, noted in the lowest member was found in the course 

 of three different traverses, two of which were seven miles apart; the bed is 

 notably persistent, but as yet does not promise a commercial quantity of iron 

 ore. The maximum thickness of the magnetite was found on the summit of 

 the ridge, 2,000 yard9 northeast of the Boundary monument at the south fork 

 of the Salmon river. 



Apparently at the same horizon a similar though much thinner (two-inch) 

 zone of crystallized, granular magnetite was found on the ridge north of Lost 

 creek and on the line of strike from the former locality. 



Under the microscope the quartzites are seen to be composed of the usual 

 clastic grains of quartz, often secondarily enlarged and regularly cemented by 

 infiltrated silica and by subordinate sericite. Unfortunately, no specimen was 

 collected from the feldspathic phases, so that the species of feldspars have not 

 been determined. The clastic quartz grains average about 0-3 mm. in diameter. 

 The metargillites of the lower members are yet more compact masses of quartz, 

 chlorite and sericite, with accessory biotite and magnetite; the micaceous 

 minerals, though all of metamorphic origin, lie with their basal planes parallel 

 to the bedding, so that the metargillitic character is typically represented. 



Higher up in the 'sections, where true dynamic metamorphism has locally 

 affected the beds, the metargillites are largely replaced by phyllites. On the 

 ridge running eastward from Lost mountain, the phyllites (probably because 

 of the influence of the Lost Creek granite magma) are charged with numerous 

 crystals of andalusite and with much metamorphic biotite. Southeast of Bee- 

 hive mountain similar, undoubtedly thermal, metamorphism has developed 

 much cyanite in small crystals disseminated through the phyllitic beds. 



