2lbs 6.9oz Wolframite & Zinnwaldite in Topaz Greisen • Koch Shaft MO • Cox Coll. For Sale

• ​Locality: Koch Shaft, Silver Mines District, Madison County, Missouri

• ​Provenance: Ex. Cox Collection

• ​Primary Minerals: Wolframite, Zinnwaldite, Topaz, Quartz

• ​Rock Type: Greisen (Hydrothermally Altered Granite)

• ​Weight: 2 lbs 6.9 oz

• ​Dimensions: 4.75\" x 3.5\" x 2.75\"

• ​Condition: Raw, natural field-collected state

​Historic Provenance: The Cox Collection

Welcome to KeepsCache. We are proud to offer this massive, incredibly dense 2 lb 6.9 oz reference specimen from the historic Koch Shaft in the Silver Mines District of Missouri. Formerly housed in the noted Cox Collection, this is an advanced, old-stock geological specimen that perfectly captures the violent magmatic-hydrothermal history of the St. Francois Mountains.

​The Greisen Assemblage

This unpolished cabinet block is a textbook example of a high-temperature \"greisen\"—formed when superheated, fluorine- and lithium-rich fluids absolutely cooked the native Precambrian granite.

• ​The Heavy Metal (Wolframite): The sheer density of this specimen is staggering. Hidden beneath the natural, rusty oxidation are exceptionally heavy, dark masses of Wolframite (Tungsten ore). This extreme specific gravity is the hallmark of premium Koch Shaft ore.

• ​The Mica (Zinnwaldite): Distinct, silvery-dark, micaceous flaking is highly visible throughout the matrix. This is Zinnwaldite, a rare lithium-iron mica intrinsically tied to these extreme high-temp vein systems.

• ​The High-Temp Silicates (Topaz & Quartz): Locking the heavy metals and micas together are structural masses of glassy, hydrothermal quartz intergrown with high-hardness Topaz, providing a stark, crystalline contrast against the heavy, iron-stained matrix.

​This is not a standard surface rock; it is a complex, heavy-metal hydrothermal anchor piece. For the serious collector of midwestern mining history, localized St. Francois geology, or rare tungsten ores, this Cox Collection specimen is a top-tier dir=\"ltr\" style=\"margin-top:0; margin-bottom:0;\">Koch Shaft ore, Silver Mines Missouri, Cox Collection minerals, KeepsCache, Madison County MO, St. Francois Mountains geology, raw wolframite, tungsten ore, zinnwaldite mica, topaz greisen, hydrothermal alteration, heavy metal ore, midwest rockhound, unpolished cabinet mineral, historic mining artifact.