Galena commonly occurs as granular masses with many shiny surfaces. It also occurs with cubic, cubo-octahedral and octahedral crystals. Galena crystals are opaque with a rich metallic luster. It blackens with time as a result of oxidation.
The largest lead and zinc deposits in the United States are located in the Tri-State mining district (Missouri, Kansas, Oklahoma) near Joplin, Missouri. This particular specimen is from the Westfork Mine in Reynolds County, Missouri, which is located in the center of the southeast quadrant of the state. That's a roll of 35mm film included in the picture to establish the scale of this specimen. The crystal has a longest edge of four and a half inches and tips the scales at eighteen and a half pounds. As I said, it's "heavy lead"! ;)
Marcasite is a common mineral which occurs in low temperature hydrothermal veins, often in association with lead and zinc sulfides. It also occurs in sedimentary deposits as a precipitate created by the action of acid waters in reduction zones. Marcasite is dimorphic with Pyrite.
Marcasite occurs as flattened prismatic crystals which are often twinned. It commonly occurs as concretionary, massive, nodular, or radiate aggregates with an opaque, greenish tinged yellow color and a metallic luster.
Large amounts of marcasite are found in the United Sates in the Tri-State mining district
and Galena, Illinois. Marcasite has industrial uses in the production of sulfuric acid.
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