Calcite Crystal with Organic Inclusions, Linwood Mine, Buffalo, Scott County, Iowa

Contributed by: Chris Clemens
Date: Apr 27th, 2026
Locality: Linwood Mine, Buffalo, Scott County, Iowa, USA (See on Mindat)

Description:
These macro photographs show a very interesting multi-wavelength fluorescent response in a single, modified scalenohedral calcite crystal, part of a much larger specimen from the Linwood Mine, Buffalo, Scott County, Iowa. Under both longwave and shortwave UV, the crystal glows white from within, and this zone of fluorescence corresponds to an internal tan/brown region within the basal half of the crystal, evidence of a likely organic activator. The tan region can be clearly seen in the visible light photograph. Under shortwave UV the surrounding smaller crystals also fluoresce a beautiful soft pink, due to a probable inorganic activator such as manganese/lead. The dark inclusions are small marcasite crystals. The main crystal in the photograph is approximately 13 mm in length.

Originally posted by Chris Clemens on Nature's Rainbows in 2017.

Fluorescence under longwave UV light.

Fluorescence under shortwave UV light.

Normal light.

Summary of luminescence responses:

Calcite (Mindat) (RRUFF)

• Fluorescence under Longwave (365nm LED) UV light: White
• Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Pink