Pegmatite/Feldspar, Coosa Co., AL
Contributed by: FMS Admin
Date: Mar 1st, 2026
Locality: Coosa County, Alabama, USA (See on Mindat)
Size: 8 x 4 x 9 cm
Weight: 270 g
Description:
Here is a feldspar-rich specimen of pegmatite that was found on a remote logging road where a bulldozer had broken through a steep bank to make the road. The bank contained a large deposit of eroding pegmatite, much of which sported this beautifully fluorescent feldspar. I have no idea exactly what kind of feldspar this is -- maybe someone else can tell me. It fluoresces under both LW and SW, but only the SW version appears here, along with the room-light image. The slight reddish hue that appears in the otherwise bluish fluorescence is not source reflection or a photographic artifact; it is a genuine fluorescence response that is probably caused by the presence of a minor second activator (e.g., divalent iron?) in some parts of the stone.
Originally published by Bill Fowler on Nature’s Rainbows.
Summary of luminescence responses:
Feldspar (Mindat) (RRUFF)
- Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Blue