64 SLATE DEPOSITS \NP IMM'STKY OF UNITED STATES, 
dips 90°. There are vertical dip joints, horizontal joints, and one diagonal one. 
The grain is parallel to the horizontal jointing, so that the slate has to be sawn in a 
northwest and southeast vertical direction and split ("sculped") in a horizontal one. 
rhe slate is very dark gray; to the unaided eye has a finer texture and liner cleav- 
.._ - ..face than that of the Monson Pond quarry, and also more luster. It is slightly 
graphitic, has very little magnetite, hut the sawn edges show considerable pyrite. It 
does not effervesce with cold dilute hydrochloric acid, and is very sonorous. 
Under the microscope this slate shows a matrix of muscovite (sericite), with a 
very brilliant aggregate polarization. There are lenses of biotite and quartz, or of 
quartz with a nucleus of pyrite, measuring up to 0.565 by 0. 14 mm., rarely 1 by (1075. 
Quartz fragments, unusually abundant in sections parallel to cleavage, measure up 
to 0.064 mm.: biotit< 9cales about IS to each square millimeter, measuring up to 
0.13 by 0.028 nun., lie a. i as - U as in the cleavage. Little less abundant than 
these are scales of chlorite interleaved with muscovite. lying across the cleavage and 
- iring up to 0.13 by 2 mm. There are also about 300 lenses of pyrite to each 
square millimeter, with their long axes in the cleavage, and measuring from 0.002 
up to 0.004 mm. in length, and up to 0.047 in width and breadth. This number 
probably includes a few crystals of magnetite. These lenses are sometimes sur- 
rounded by secondary muscovite. Generally distributed is a dark grayish or black 
material, probably graphitic, to which the slate owes its blackness. Tourmaline 
prisms up to 0.047 by 0.009 mm. No carbonate was detected. 
The relative abundance of these minerals appears to be, in descending order, museo- 
aiartz. biotite. chlorite, pyrite. graphite, and magnetite. 
The product is at present being prepared exclusively for rooting. 
—At the quarry of the Monson Consolidated Slate Company a bed of 
black slate feet thick, with a bed of quartzite 15 feet thick on its north side, and 
small alternating beds of quartzite and slate on its south side an- exposed, the whole 
- measuring perhaps I The quarry in 1004 measured 300 feet along the 
strike. ss it. and U pth. The walls are supported by three pillars of 
slate. Bedding and _ oth strife . . and dip 00° K. There are vertical 
dip joints striking N. 15° W.; also horizontal joints to which the grain is parallel. 
There are about 15 feet of till on the edges of the glaciated slate. As only on^ bed 
slate if tageofwast at this quarry is very small. 
The slate is a very dark gray. To the unaided eye texture and cleavage surface 
are very fine. It has more luster than the Pond quarry slate, but not as much as 
that of the Maine Slate Company of Monson. It is slightly graphitic, has no magnet- 
it shows pj beons _ - s not effervesce with cold dilute hydrochloric^ 
acid, and - - norous. 
Under the mi - this slate shows a matrix of mus sericite with a 
brilliant aggregate polarization. There are a few lenses of quartz and biotite, nieas- 
_ from O.b " " .034 mm.. some lying in the cleavage, others in the 
tionof the grain. The quartz fragments measure up t<> 0.02 by 0.012. There 
are about nine bio: " - - I each square millimeter, measuring up to 0.08 by 
- about fourteen chlorite sea.- - - iring 0.047 by 0.02 mm., but 
sometime? 85 b; with their longer axes and lamina- usually parallel to the 
cleavage and across the grain: and finally, twenty to fifty lenses and crystals of 
pyrite to each square millimeter, measuring, in seel 1 ss the cleavage, up to 
0.066 . with their longer axes parallel to the cleavage, and the usual finely 
.rbonaceous matter: also tourmaline prisms up to 0.007 by 0.008 mm. 
N arbonate was detected. 
The probable relative abundance of these constituents, in descending order, is mus- 
. quartz, chlorite, pyrite. biotite. and cai as matter or graphite] 
Merrima: '- tests : this slate are given on pagi 
This slate is as tfing and mill stock, particularly for electric pur: - - 
