Purple Fluorite From Elmwood Mine

Purple Fluorite On Dolomite, From the Elmwood Mine, Smith County, Tennessee.

The Elmwood Mine, part of the extensive Mississippi Valley-Type (MVT) deposit system in Smith County, Tennessee, developed within carbonate host rocks of Ordovician age. These sedimentary formations—primarily dolostone—formed in a shallow marine environment over 450 million years ago. Tectonic activity and associated hydrothermal processes during later orogenic events mobilized mineral-rich fluids through the porous and fractured carbonate strata.

Purple Fluorite On Dolomite, From the Elmwood Mine, Smith County, Tennessee.  Credit: The Mineral Gallery, Inc.

Fluorite Crystallization:

Fluorite (CaF₂) precipitated from these hydrothermal fluids as they moved through voids and fissures in the dolostone. The fluids were enriched in calcium and fluorine, likely sourced from deeper sedimentary or evaporitic sequences. Within these open spaces, fluorite crystallized into sharply defined cubes, occasionally exhibiting stepped growth patterns or internal zoning—often referred to as "phantoms"—where concentric color bands mark distinct episodes of crystal growth. Some fluorite crystals display hollowed or etched forms, locally known as “Carthage corners,” shaped by partial dissolution and recrystallization during later fluid episodes.

Color and Morphology:

The Elmwood fluorite is renowned for its saturated purple to lavender hues, a result of trace element substitution (notably yttrium and rare earth elements) and radiation-induced color centers. Under directed lighting, these crystals can exhibit remarkable internal glow and translucency, with darker zoning near the cube edges. While purple is dominant, specimens may also show colorless to pale blue variations, depending on the geochemical conditions at the time of formation.

Purple fluorite cubes with translucent edges on matrix from Elmwood Mine, Tennessee, USA. Photo: McDougall Minerals..

Dolomite Association:

Fluorite crystals are commonly perched on beds of white to pale gray dolomite, which crystallized earlier from magnesium-rich fluids under low-temperature conditions. This dolomite matrix provides a contrasting backdrop that highlights the cubic geometry and vibrant color of the fluorite. The combination of fluorite atop sparkling dolomite enhances the visual and mineralogical appeal of these specimens.

Accessory Minerals:

Accompanying the fluorite-dolomite assemblage are crystals of rubyjack sphalerite—an iron-rich variety of ZnS that adds reddish to amber hues to the matrix. These formed from the same hydrothermal systems, often in overlapping stages of deposition, and contribute to the Elmwood Mine’s reputation for multicolored, highly aesthetic mineral combinations.

Fluorite cubes with phantoms from Elmwood Mine, Tennessee

Though hosted in ancient Ordovician dolostone, the fluorite crystals from Elmwood formed significantly later, through post-depositional hydrothermal processes. The interplay of mineral-laden fluids, open-space crystallization, and evolving geochemical conditions produced some of the world’s most striking fluorite specimens—defined by clarity, intense coloration, and complex associations with dolomite and sphalerite.