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Einstein Silver Mine — Koch Shaft Polymetallic Greisen
Ex. Cox Family Collection · Madison County, Missouri
Roughly 1.47 billion years ago, the granite that would become the St. Francois Mountains was invaded by its own dying breath. As the pluton cooled, the last fraction of melt concentrated everything the crystallizing rock would not accept — fluorine, tungsten, arsenic, lead, silver — into a superheated vapor that tore upward through the fractures it had just made. Where that vapor met solid granite, it destroyed it. Feldspar dissolved. Mica rebuilt itself as lithium-bearing zinnwaldite. Quartz and topaz grew in the wreckage. What was left is greisen: a rock made entirely out of the chemical violence of its own alteration.
Then the metals came. Arsenopyrite and pyrite bearing gold in varying amounts crystallized in the voids. Wolframite laid down black bladed tungsten ore. Galena arrived carrying high concentrations of silver that gave this stretch of the St. Francis River its name. Fluorite crept in as violet films along the last open seams. Much later — a billion years later — groundwater found the vein and began taking it apart, replacing iron sulfide with limonite and goethite and leaving the deep amber-orange rind that wraps the right side of this piece.
This specimen is a cross-section straight through that entire sequence. The polished face reads left to right like a timeline: greisen groundmass in cream and olive, swarms of dark sulfide and wolframite in the middle, and the oxidized gossan front on the outer edge. Angular fragments of topaz-quartz greisen sit suspended within the sulfide masses — evidence the vein was shattered and re-cemented while mineralization was still underway. Salmon-pink relict feldspar survives in patches where the alteration front never finished its work.
Minerals present:
wolframite (tungsten ore) · argentiferous galena ( silver ore) and carrying small amounts of gold ( arsenopyrite · pyrite )· fluorite · goethite · limonite · topaz · quartz · zinnwaldite (lithium mica) · chlorite · relict K-feldspar sphalerite
Fluorescence: This piece shows a genuine UV response — a discrete white-cream spot on the polished face (center right, roughly halfway up), orange fluorescence following a vein on the face and embedded in the limonite on the reverse, and scattered violet-pink points consistent with fluorite. The orange phase does not react to dilute acid, ruling out calcite. Powellite, apatite, and scheelite are all plausible candidates given the district's documented mineralogy. These phases are unconfirmed and are not claimed as identified species — the fluorescent response is offered as an observation for the buyer to pursue.
Dimensions: 5" tall × 2.625" wide × 1.5" deep
Weight: 642 grams (1 lb 6.7oz)
Preparation: One polished face, cut base — stands unaided
Locality: Koch Shaft, Einstein Mine, Silver Mine, Fredericktown Mining District, Madison County, Missouri
Provenance: The Cox Family Collection
The Koch Shaft has been closed and plugged for generations. This piece comes from the last box of Koch Shaft material in my hands, and when it is gone there is no resupply — not from me, and most likely not from anyone.
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