ARKANSAS. 55 
The chief constituents, arranged in the descending order of abundance, appear 
to be muscovite (sericite), quartz, kaolin, chlorite, rutile, pyrite, magnetite, and 
tourmaline. 
This is a very superior siate on account of its fissility, color, and freedom from 
carbonate, but its strength and resistance to frost should be tested. 
Very dark bluish gray slate from sec. 25, T. 3 S., R. 29 W. (Specimen collected by 
Mr. E. C. Eckel. ) 
To the unaided eye this slate has a fine texture and a smooth cleavage surface with 
a little luster, and shows a litt'e pyrite on the sawn edge. It contains very little 
magnetite, considerable carbonaceous or graphitic matter, does not effervesce with 
cold dilute hydrochloric acid, is sonorous, and has a high grade of fissility. Under 
the microscope it shows a line-textured matrix of muscovite (sericite) with good 
aggregate polarization, but somewhat obscured by carbonaceous matter. Quartz is 
not abundant, the grains measuring up to 0.047 by 0.02 mm. Pyrite spherules, meas- 
uring up to 0.008 mm. in diameter, number about 120 per square millimeter. There 
are rutile needles but no carbonate. 
The chief constituents, arranged in order of decreasing abundance, appear to be 
muscovite (sericite), quartz, pyrite, carbonaceous or graphitic matter, and rutile. 
This slate has absence of carbonate in its favor. It is not so fine textured or so fis- 
sile as that described on page 53, but may prove more durable. 
Light-gray slate with a slightly greenish tinge from sec. 30, T. 3 S., R. 28 W. 
(Specimen collected by Mr. E. C. Eckel.) To the unaided eye this has a fine tex- 
ture, but a lusterless, roughish surface, and shows a little pyrite on the sawn edges. 
It contains an insignificant amount of magnetite but no carbonaceous or graphitic 
matter, does not effervesce with cold dilute hydrochloric acid, and has an argilla- 
ceous odor and a fair degree of fissility and sonorousness. 
Under the microscope it shows a fine-textured matrix of muscovite (sericite) with 
brilliant aggregate polarization, containing not abundant quartz grains, measuring 
up to 0.03 mm., scales of chlorite and of muscovite transverse to cleavage, some 
pyrite cubes up to 0.063 mm. (generally with a rim of secondary quartz) passing into 
limonite and staining the matrix. Rutile needles abound. 
The chief constituents, arranged in decreasing order of abundance, appear to be 
muscovite (sericite), quartz, chlorite, kaolin, pyrite, rutile, and limonite, with acces- 
sory magnetite. 
Whether the limonitic staining from the decomposition of the pyrite will produce 
any appreciable discoloration in the course of years can be determined only by 
experiment. ^, 
Very dark-gray spangled slate from quarry operated by the Southwestern Slate Manu- 
facturing Company. (Specimen collected by Mr. E. C. Eckel.) To the unaided eye 
this has a coarsish texture and a roughish, almost lusterless surface, spangled with 
minute scales of mica, shows pyrite on sawn edges, contains very little magnetite and 
little carbonaceous matter, does not effervesce with cold dilute hydrochloric- acid, is 
somewhat sonorous, tolerably fissile, and has a slight argillaceous odor. 
Under the microscope it shows a fine-textured matrix of muscovite (sericite) with 
brilliant aggregate polarization, containing roundish and angular grains of quartz of 
variable and large size, even up to 0.27 by 0.17 mm.; also a few of plagioclase feld- 
spar, scales of muscovite and biotite up to 0.2 by 0.1 mm., some lenses of carbonate 
up to 0.4 long, a few grains of tourmaline, and lenses of secondary quartz. There 
is a faint incipient false cleavage, not apparent, however, in the hand specimen. 
The chief constituents of this slate, arranged in order of decreasing abundance, 
appear to be muscovite (including sericite), quartz, carbonate, pyrite, carbonaceous 
matter, and kaolin, with accessory biotite, plagioclase, tourmaline, and magnetite. 
This slate combines some of the features of a metamorphic gray wacke or grit with 
those of a mica-slate. It is inferior to the dark bluish-gray slate described above. 
Bull. 275—06 5 
