Ch. 1: Geology of Maine Pegmatites

Ch. 1: Geology of Maine Pegmatites Page of 170 Ch. 1: Geology of Maine Pegmatites Text size:minus plus Restore normal size   Mail page  Print this page
MINERAL AND CHEMICAL COMPOSITION.
17
Emerald.—Gem beryl found in Maine is usually so pale that it is classed as aquama­rine. One fractured crystal found by the 'writer at the Dunton mine in Newry could properly be classed as a pale emerald.
Feldspar.—One of the principal pegmatite minerals. See albite, orthoclase, and microcline.
Fluorite.—Small crystals occur as an original constituent in a few of the pegmatites, but in general fluorite is much rarer in the Maine pegmatites than in those of certain other regions.
Garnet.—A common constituent of most of the pegmatites. Frequently occurs in graphic intergrowth with quartz, muscovite, or feldspar. Garnet of gem clearness is extremely rare.
Graphite.—Absent from most of the Maine pegmatites. Occurs in pegmatite injected into sedimentary schists at a few localities.
Gummite.—Reported in minute particles from pegmatite at Mount Apatite, in Auburn. An alteration product of some uranium mineral.
Halloysite.—Reported from Mount Mica. Probably a decomposition product of feldspar.
Hamlinite.—Occurs sparingly at Stoneham, associated with herderite and ber-trandite.
Hebronite.—See Amblygonite.
Herderite.—Found at Stoneham, Me., on quartz crystals in pockets in the pegmatite. Found sparingly in Hebron and Greenwood, at Mount Apatite in Auburn, and at Berry's quarry in Poland.
Kaolinite.—A decomposition product of feldspar. Common in pockets in the coarser pegmatites.
Limonite.—A secondary mineral in some pegmatites, resulting from the decomposi­tion of other iron-bearing minerals.
Lepidolite.—Common in pegmatites which bear gem tourmalines. Lollingite.—Occurs in narrow stringers cutting feldspar at Mount Mica, in Paris, as an original pegmatite constituent. Magnetite.—Common in many pegmatites in well-developed step-crystals. Microcline.—One of the commonest constituents in the pegmatites. Most of the potash feldspar present is microcline rather than orthoclase. Mica.—See Biotite, Muscovite, and Lepidolite.
Molybdenite.—Abundant as an original constituent in granite and associated pegma­tite at Catherine Hill in Hancock County, and reported in small amounts in similar rocks elsewhere. Reported from pegmatite in Auburn. Rare in most pegmatite bodies.
Montmorillonite.—Associated with cookeite and other secondary minerals in the pock­ets of several of the coarser pegmatite masses. A product of feldspar decomposition. Muscovite.—One of the principal constituents in nearly all pegmatites. Orthoclase.—Present with microcline in nearly all of the pegmatites, the two being commonly intergrown in the same crystal. Phenacite.—Reported from pegmatite at Noyes's tourmaline mine in Greenwood. Plumbago.—See Graphite.
Pollucite.—Occurs in pockets in pegmatite at Mount Rubellite in Hebron. Pyrite.—An original constituent in many Maine pegmatites.
Pyrrhotite.—An original pegmatite constituent at Mount Mica, in Paris, and at a few other localities.
Quartz.—White or gray, one of the principal constituents of all the pegmatites. Massive rose quartz occurs in a few places and crystal groups of amethystine and smoky quartz are developed here and there on the walls of pockets in the pegmatite. Rhodochrosite.—An original pegmatite constituent at the Towne quarry in Auburn. 63096°—Bull. 445—11------2
Ch. 1: Geology of Maine Pegmatites Page of 170 Ch. 1: Geology of Maine Pegmatites
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