Dumortierite - Dehesa, California

Contributed by: Chris Clemens
minID: AU3-NM5
Date: May 21st, 2026
Locality: Dehesa Dumortierite deposit (Lehesa Dumortierite deposit), Alpine, Laguna Mountains, San Diego County, California, USA (See on Mindat)
Size: 55 x 45 x 73 mm
Weight: 192 g

Description:
Dumortierite is an aluminum iron borosilicate mineral that does not get much attention in the world of fluorescence, but is a lovely fluorescent species, nonetheless. This specimen is from the Dehesa Dumortierite deposit, Alpine, Laguna Mts, San Diego County, California, and consists of radiating sprays and inclusions of purple, grey dumortierite in a milky quartz matrix. The dumortierite is reactive under shortwave UV, and shows a bright blue-white, fluorescent response.

Originally posted by Chris Clemens on Nature's Rainbows in 2021.

Fluorescence under shortwave UV light.

Normal light.

Summary of luminescence responses:

Dumortierite (Mindat) (RRUFF)

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