Zinc Minerals Willemite and Smithsonite from Tsumeb, Namibia.

Contributed by: FMS Admin
Date: Feb 28th, 2026
Locality: Tsumeb, Oshikoto Region, Namibia (See on Mindat)
Size: 5 x 3.5 x 8 cm
Weight: 255 g

Description:
Green Willemite and white, tan Smithsonite as described in Robbins (1994). Willemite covers about half of the surface of the specimen and consists of several crystals (most of them sub-millimeter). There are several cavities/vugs.

Willemite fluorescence:
• Yellow under LW and MW (best in MW)
• Sky-blue in SW
• Very phosphorescent

Smithsonite covers the other side. Hundreds of white and tan crystals of about 1mm fluoresce a vivid blue under SW. Purple hue is also evident. MW and LW are not significant. Strongly phosphorescent after SW. Purchased at the Vienna Mineral show for 20€. ()

Originally posted by Stefano Buzzoni on Nature's Rainbows.

Fluorescence under longwave UV light.

Fluorescence under shortwave UV light.

Afterglow after exposure to shortwave UV light.

Normal light.

Fluorescence under shortwave UV light. Closeup of willemite crystals.

Fluorescence under shortwave UV light. Side 2 - smithsonite (blue).

Normal light. Side 2.

Summary of luminescence responses:

Willemite (Mindat) (RRUFF)

• Fluorescence under Longwave (365nm LED) UV light: Yellow
• Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Blue
• Afterglow after exposure to Shortwave (254nm Lamp/Mercury) UV light: Blue

• Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Blue