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Weighing 2 pounds 13.4 ounces and measuring 6\" x 4\" x 2.5\", this is a massive, mineral-dense display specimen of classic greisen from the famous Koch Shaft. Sourced directly from the historic Cox Family Collection, this piece has been custom-cut in the shop to stand upright for display, with the primary face polished smooth to reveal a rich cross-section of hydrothermal mineralization.
The polished face provides a detailed look into the complex ore matrix:
- Argentiferous Galena & Sulfides: Disseminated grains of silver-bearing galena and trace chalcopyrite are locked throughout the matrix, highlighting the primary metallic ores mined in the district.
- Wolframite: Sharp, stark black, sub-metallic crystals of wolframite stand out vividly against the lighter matrix.
- Zinnwaldite Mica: Abundant greenish-brown to dark platy flakes of lithium-bearing mica form a major part of the altered greisen matrix.
- Quartz & Granular Topaz Groundmass: The durable crystalline matrix locking the specimen together consist of quartz intergrown with high-hardness granular topaz.
- Iron Oxide Veining: Natural rust-orange hematite/limonite staining tracks through micro-fractures across the polished face, framing the mineral inclusions.
Dimensions: 6\" wide x 4\" tall x 2.5\" deep
Weight: 2 lbs 13.4 oz
Locality: Koch Shaft, Einstein Silver Mine District, Madison County, Missouri
Provenance: The Cox Family Collection
The History & Geology
The Koch Shaft of the Einstein Silver Mine District is legendary among Midwest mineral collectors for its unique high-temperature hydrothermal vein system. Greisen forms through the intense alteration of granite by superheated, fluorine-rich volcanic fluids, resulting in a complex cocktail of rare minerals. A thick, cut-and-polished cabinet piece of this weight—showing galena, wolframite, and lithium mica together—serves as a complete geological snapshot of historic Missouri silver and tungsten dir=\"ltr\" style=\"margin-top:0; margin-bottom:0;\">Koch Shaft Missouri, argentiferous galena, wolframite crystal, greisen matrix, Cox Family Collection, Silvermines MO, zinnwaldite mica, KeepsCache lapidary, cut base display, Missouri silver ore, mineral specimen, tungsten ore, Madison County geology.
