Dumortierite - Alpine, California

Contributed by: Chris Clemens
Date: Apr 29th, 2026
Locality: Dehesa Dumortierite deposit (Lehesa Dumortierite deposit), Alpine, Laguna Mountains, San Diego County, California, USA (See on Mindat)
Size: 29 x 18 x 44 mm

Description:
Purple dumortierite in a light-colored quartz groundmass, from the Dehesa Dumortierite deposit, Alpine, Laguna Mountains, San Diego County, California. The small, needle-like dumortierite crystals show a crisp blue/white, fluorescent response under shortwave UV. Dumortierite is a fibrous aluminum boro-silicate mineral.

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

Fluorescence under shortwave UV light.

Normal light.

Summary of luminescence responses:

Dumortierite (Mindat) (RRUFF)

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