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The Leadville Mill M 1990 -057 EXHIBIT B — SITE DESCRIPTION Page 3 -3 the intrusion of the porphyry and before the uplift of the range. In the uplift of the range both eruptive sheets and sedimentary beds, with the included ore deposits, were plicated and faulted, and by subsequent erosion an immense thickness of rocks has been carried away, laying bare the very lowest rocks in the conformable series; the outcrops are, however, frequently buried beneath what is locally called "wash," a detrital formation of glacial origin. In the Leadville region, owing to the reduplication caused by faulting, a series of outcrops of easterly dipping beds of the Blue Limestone are exposed beneath the wash, of which all are metalliferous and a considerable proportion carry pay ore. The district is a highly faulted area; intruded with Tertiary quartz monzonite porphyries, on the east side of the Arkansas River graben, part of the Rio Grande Rift system. The silver occurs associated with manganese and lead in veins, stock works, and manto -type deposits in the Mississippian Leadville Limestone (here a dolomite), the Devonian Dyer Dolomite, and the Ordovician Manitou Dolomite. Ore minerals are pyrite, sphalerite, and galena, in jasperoid and manganosiderite gangue. In upper levels, the ore minerals are oxidized to cerussite, anglesite, and smithsonite. The site is located between the Mosquito Range to the east and the Sawatch Range to the west in Southern Rocky Mountain province. The province elevation ranges from 6,000ft to over 14,000ft. The rocks range in age from the Precambrian (950 to 1,800 million years old) consisting of igneous and metasediments largely granites, gneiss, and schist; and geologically recent Tertiary volcanic and intrusive rocks. The units are fractured crystalline aquifers that supply most of the domestic needs in the mountainous portion of the state. (Groundwater Atlas of Colorado, 2003). 3.3 ORE DEPOSITS The principal ore deposits of Leadville occur, as above indicated, in the Blue Limestone and at or near its contact with the overlying bodies of porphyry. The ores consist mainly of carbonate of lead, chloride of silver and argentiferous galena, in a gangue of silica and clay, with oxides of iron and manganese and some barite. These materials are mainly of secondary origin, and result from the alteration by surface waters of metallic sulfides. The study of these deposits has shown: Version 1.0 April 2013