Fluorescent Mineral Database

A new secret project! Trying to create a nice Fluorescent Mineral Database (FMDB), which would be searchable by mineral, locality, and luminescence properties. Also making it easy for people to contribute with their own specimens!

Fluorescent and Phosphorescent Thenardite from Soda Lake, California

Contributed by: FMS Admin
Date: Feb 24th, 2026
Locality: Soda Lake, Carrizo Plain, San Luis Obispo County, California, USA (See on Mindat)
Size: 2.25 x 2 x 4 inches
Weight: 10 oz

Description:
Thenardite is an anhydrous sodium sulfate mineral which occurs in arid evaporative environments such as Soda Lake. It fluoresces in a ghostly blue fashion and is best under shortwave ultraviolet light. It phosphoresces blue as well. Only shortwave ultraviolet pictures are posted in addition to a daylight one. Long and Midwave fluorescence are similar but not as vivid as that of shortwave.

Fluorescent pictures were taken at ISO-100, f/11 for 1.3 seconds.

Originally posted by John Rofrano on Nature's Rainbows.

Fluorescence under shortwave UV light.
Fluorescence under shortwave UV light.
Afterglow after exposure to shortwave UV light.
Afterglow after exposure to shortwave UV light.
Normal light.
Normal light.
Fluorescence under shortwave UV light. Closeup
Fluorescence under shortwave UV light. Closeup
Fluorescence under shortwave UV light. Side 2
Fluorescence under shortwave UV light. Side 2

Summary of luminescence responses:

Thenardite (Mindat) (RRUFF)

  • Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Blue
  • Fluorescence under Midwave (305nm Lamp/Mercury) UV light: Blue
  • Fluorescence under Longwave (365nm LED) UV light: Blue

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