Ch. 2: Maine Pegmatites: Local Descriptions

Ch. 2: Maine Pegmatites: Local Descriptions Page of 170 Ch. 2: Maine Pegmatites: Local Descriptions Text size:minus plus Restore normal size   Mail page  Print this page
OXFORD COUNTY.                                                 97
the pegmatite contacts studied. It has resulted in the abundant development of prisms of cinnamon-brown tourmaline from one-fourth to one-half inch long and one-sixteenth to one-eighth inch in diameter in certain of the more muscovitic layers. More biotitic portions present a mottled appearance, due to the occurrence of the biotite, in irregular aggregates one-eighth to one-fourth inch in diameter. Under the microscope this mottled rock is seen to con­sist of brown biotite, light-green hornblende, quartz, labradorite, titanite, magnetite, and apatite, the latter in small hexagonal prisms filled with a cloud of very minute inclusions. The tendency to ag­gregation of the biotite, hornblende, titanite, and magnetite gives the mottled appearance, the white intervening areas being largely quartz and labradorite. The mineral grains of this rock are inter­locking and the texture granular and indistinguishable from that of an igneous rock. Field relations show, however, that the rock is a phase of the sedimentary schist wall rock which has undergone complete recrystallization.
It is notable that neither of the metamorphosed phases of the wall rock described above contains any minerals except the common ones, quartz and muscovite, that are characteristic of the neigh­boring pegmatite. The tourmaline, of the schist is brown and wholly dissimilar from any found in this or any other pegmatite of the State. Additions, if any, received by the wall rock from the peg­matite during the complete recrystallization of the former were ionic in their character, the minerals characteristic of the pegmatite, with the possible exception of quartz, not being added as such to the intruded rock.
The quarry was opened in about 1901 by Oliver Gildersleeve and has been worked for four seasons. About 250 tons of mica is reported to have been mined in 1905. The quarry was idle through­out 1906, in which year the writer visited it, and so far as is known has not reopened since. Steam drills were employed and sheds built for hand picking the mica, which was packed in 100-pound bags and hauled by team 7 miles to Frye, on the Rangeley division of the Maine Central Railroad. From Frye it was shipped to a grinding mill at Gildersleeve, Conn. About 1,000 tons in all are reported to have been shipped. The quantity of scrap, mica still available at this quarry is large, but there is no plate mica, nor is it probable that further excavation will disclose any. It is doubtful if at present the property can be profitably exploited for scrap mica in view of the fact that the refuse cuttings from plate mica properties appear able to meet entirely the present demand for scrap mica. 63096°—Bull. 445—11------7
Ch. 2: Maine Pegmatites: Local Descriptions Page of 170 Ch. 2: Maine Pegmatites: Local Descriptions
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