Miserite from Arkansas
Contributed by: Douglas Bank
Date: Jun 10th, 2025
Locality: North Wilson pit, Union Carbide Mine, Wilson Springs (Potash Sulfur Springs), Garland County, Arkansas, USA (See on Mindat)
Size: 5 x 4 x 10 cm
Weight: 199 g
Description:
This 10 × 5 × 4 cm (199 g) specimen features pink miserite crystals embedded in a pale, granular matrix dominated by wollastonite. Under white light, the miserite displays a muted but unmistakable pink hue, contrasting with the lighter matrix. Under ultraviolet light, the miserite fluoresces yellow under shortwave UV, while remaining non-responsive (black) under longwave and midwave. The wollastonite exhibits its own fluorescent response: orange under shortwave, a brighter orange under midwave, and a paler wash under longwave. Scattered patches of bright blue fluorescence suggest the presence of additional, unidentified accessory minerals, possibly contributing to the specimen’s complexity and character.
Though originally labeled “Magnet Cove,” the mineral assemblage and fluorescence behavior strongly point to the North Wilson Pit as the more precise source. Located just west of the main Magnet Cove complex, the North Wilson Pit (also referred to as the Wilson Springs area) is the only confirmed locality in Arkansas for miserite, a rare potassium-calcium silicate. Similar specimens—such as one from the Harvard Mineralogical Museum (catalog no. 123824)—were historically labeled “Magnet Cove,” but have since been reattributed to Wilson Springs on Mindat, reflecting evolving knowledge of locality boundaries and mineral occurrences. Though the original label also mentioned magnetite and brucite, these minerals do not appear to be present in this particular piece.
The specimen is mildly radioactive, with consistent readings of 0.3–0.5 µSv/hr across the surface. Portable XRF scans indicate 70–100 ppm uranium throughout the specimen, which may contribute both to the miserite’s fluorescence and to the overall radioactivity. While not dangerous with casual handling, the reading is elevated above background and typical of minerals associated with metasomatic systems that brought rare silicates and vanadium mineralization to the area. These characteristics make the specimen not only visually striking but also analytically rich for collectors interested in geochemistry and paragenesis.
Radioactivity in the broader Wilson Springs region is not surprising. According to historical mining records and regional surveys—including those summarized in the Encyclopedia of Arkansas—the area was extensively mined for vanadium in the mid-20th century, and the unusual geological environment led to the formation of several rare uranium- and thorium-bearing silicates. Though miserite is not itself a primary uranium mineral, its occurrence alongside trace uranium provides both scientific and historical significance. This specimen captures the unusual chemistry, fluorescence, and locality specificity that make the North Wilson Pit one of the most mineralogically unique sites in the eastern United States.
Summary of luminescence responses:
Miserite
- Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Yellow
- Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Orange
- Fluorescence under Midwave (305nm LED) UV light: Orange
- Fluorescence under Longwave (365nm LED) UV light: Orange