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1950 BUREAU OF MINES REPORT <br />hard, pure, gray-blue dolomite, with a fine, frosty <br />luster on fresh surfaces; it is brown on weathered <br />exposures. <br />Chaffee Formation (Devonian). The Chaffee Formation <br />includes the thin Parting Quartzite member at the bottom <br />and the much-thicker Dyer [dolomite] at the top." The <br />Parting is a series of thin, green to brown dolomites <br />and dark brown shales, with white to pale-green hard <br />quartzite beds near both the top and bottom. The Dyer <br />consists of medium to thin beds of hard dolomite with a <br />rough, conchoidal fracture, gray-blue where fresh, <br />yellow to brown where weathered. <br />Leadville Limestone (Mississippian). The base of the <br />Leadville is considered to be a thin persistent sandy <br />zone with one to four 3- to 6-inch beds of dolomitic <br />sandstone and quartzite interlayered with thin <br />dolomite.'2 Immediately overlying this unit is up to 20 <br />ft. of dolomite containing numerous nodules and <br />lenticular stringers of black chert. The lower half of <br />the Leadville consists of massive, hard dolomite similar <br />to the Dyer, and the upper half is medium- to fine- <br />grained massive limestone. Fresh surfaces of the <br />limestone are frosty-blue, while it weathers to a light <br />blue smooth surface. The limestone is absent in the <br />Smuggler mine area. <br />Weber fBeldenl Formation {Pennsylvanian). The Weber <br />[Belden] is separated from the Leadville by an easily <br />recognized contact of a few feet of cherty quartzitic <br />conglomerate in a black shale matrix." The Weber <br />[Belden} is a series of thin gray to black carbonaceous <br />limestones and calcareous shales. The dark, <br />carbonaceous limestones weather to black mud. The <br />shales are weak and are commonly slickensided parallel <br />to bedding. The Weber [Belden] is distinguished by <br />universal disseminated fine pyrite cubes and many small <br />irregular veins of white crystalline calcite, both of <br />secondary origin. The upper part of the formation is <br />mainly thin micaceous gray limestone. <br />The sandy beds above the Dyer Dolomite, previously included in the <br />lower Leadville Limestone, are now named the Gilman Sandstone and are <br />considered part of the Chaffee Group, which spans the Devonian- <br />Mississippian boundary. <br />32 This is the Gilman Sandstone, see note immediately preceding <br />concerning the Chaffee-Leadville boundary. <br />Breccias I and II, see generally $TEGEN THESIS and STEGEN REPORT. <br />Hr~~e A. CO111R5 - ZQ - BIBLIOGRAPHY <br />