Calcite Crystals on Limestone Matrix - Linwood Mine, Buffalo, Scott Co., Iowa

Contributed by: Chris Clemens
Date: Apr 27th, 2026
Locality: Linwood Mine, Buffalo, Scott County, Iowa, USA (See on Mindat)
Size: 11 x 8.2 x 13.2 cm

Description:
Gemmy, modified scalenohedral, calcite crystals with marcasite inclusions, on limestone matrix, from the Linwood Mine, Buffalo, Scott County, Iowa. This specimen shows an interesting multi-wavelength fluorescent response under UV. Under shortwave UV the calcite shows moderate, pastel, pink fluorescence with isolated brighter white zones within some of the crystals. The limestone matrix is also dimly fluorescent. After the shortwave source is removed, brief blue and white phosphorescence is seen, highly zonal in nature. Under longwave UV the calcite shows a very dim pink response, but the zoned areas that responded white to shortwave UV now fluoresce brighter white. The white, fluorescent regions correspond to internal brown areas near the base of the crystals that can be seen under visible light. This suggests that the white fluorescence is caused by the presence of an organic activator. The pink fluorescence is likely due to an inorganic activator, perhaps manganese/lead.

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

Fluorescence under shortwave UV light.

Afterglow after exposure to shortwave UV light.

Fluorescence under longwave 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: Red