Prosopite, Thomsonite, Ralstonite from Ivigtut, Greenland

Contributed by: Howie Green
Date: Mar 9th, 2026
Locality: Ivigtut Mine, Ivigtut stock, Arsuk Fjord, Sermersooq, Greenland (See on Mindat)

Description:
Prosopite can form as an alteration product in cryolite-bearing pegmatites, either as a primary mineral or as an alteration product of cryolite. Shown under shortwave UV.

Originally posted by Howie Green on Nature's Rainbows.

Fluorescence under shortwave UV light.

Normal light.

Summary of luminescence responses:

Prosopite (Mindat) (RRUFF)

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