Sphalerite and Hydrozincite - Big Cottonwood Canyon, Utah

Contributed by: Chris Clemens
Date: Apr 30th, 2026
Locality: Maxfield Mine, Argenta, Big Cottonwood Mining District, Salt Lake County, Utah, USA (See on Mindat)
Size: 49 x 24 x 61 mm
Weight: 84 g

Description:
This triangular-shaped piece of waste rock was surface collected from a tailings pile at the Maxfield mine, in Big Cottonwood Canyon, Salt Lake County, Utah. It contains grains of sphalerite that fluoresce bright orange under UV, most brightly under longwave. The sphalerite is also phosphorescent and triboluminescent. One side of this specimen is coated with hydrozincite, which fluoresces blue/white under shortwave UV. Best viewed under fullwave UV lighting (SW + MW + LW) this piece shows a spectacular two-color fluorescent response.

Located in the Wasatch Mountains above the Salt Lake Valley, the Maxfield mine is a former copper, gold, lead, silver, and zinc mine that operated during the early 1900s.

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