Buttery Yellow Calcite - Elk Creek, South Dakota

Contributed by: Chris Clemens
Date: Apr 29th, 2026
Locality: Elk Creek, Meade County, South Dakota, USA (See on Mindat)
Size: 9 x 8 x 13 cm
Weight: 742 g

Description:
Best known for its golden-amber colored barite crystals, the Elk Creek area of Meade County, South Dakota, also produces buttery yellow calcite crystals that are fluorescent under all UV wavelengths. The primary occurrence of this material is located along the bank of Elk Creek in the Black Hills of Western South Dakota, where the calcite crystals have formed within the hollow interiors of calcareous concretions found in the surrounding Cretaceous age shale. The calcite shows a similar creamy honey-colored fluorescent response under all UV wavelengths, brightest under longwave.

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

Fluorescence under shortwave UV light.

Fluorescence under longwave UV light.

Normal light.

Normal light. Closeup

Fluorescence under shortwave UV light. Closeup

Fluorescence under longwave UV light. Closeup

Fluorescence under shortwave UV light. Closeup 2

Fluorescence under longwave UV light. Closeup 2

Normal light. Closeup 2

Summary of luminescence responses:

Calcite (Mindat) (RRUFF)

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