Hydrozincite and Fluorite from Santa Eulalia, Chihuahua, Mexico
Contributed by: Michael Crawford
Date: Oct 30th, 2025
Locality: Santa Eulalia Mining District, Aquiles Serdán Municipality, Chihuahua, Mexico (See on Mindat)
Size: 7.5 x 11 cm
Description:
This is some new material recently recovered (2025) from the Santa Eulalia area, Chihuahua, Mexico. The specimen contains purple fluorite (CaF2) and hydrozincite (Zn5(CO3)2(OH)6). Hydrozincite, a secondary mineral, forms through the alteration of other zinc-bearing minerals such as sphalerite, hemimorphite, or smithsonite. Observations indicate that fluorite crystallized atop the hydrozincite.
Under longwave and midwave ultraviolet light, the fluorite exhibits violet-blue fluorescence, with an emission spectrum peaking at 422 nm, characteristic of europium (Eu²?) activated fluorescence in fluorite. The hydrozincite displays bright yellow fluorescence under longwave UV and fainter yellow under midwave UV. Notably, hydrozincite fluorescence shifts to vivid light blue under shortwave exposure, with its shortwave emission spectrum presenting a broad peak at 429 nm, attributed to lead (Pb²?) substituting for zinc. The longwave emission peak for hydrozincite\'s yellow fluorescence is measured at 563 nm; however, the cause of this yellow fluorescence remains unidentified.
Summary of luminescence responses:
Hydrozincite (Mindat) (RRUFF)
- Fluorescence under Longwave (365nm LED) UV light: Yellow
- Fluorescence under Midwave (305nm Lamp/Mercury) UV light: Yellow
- Fluorescence under Shortwave (255nm LED) UV light: Blue
- Fluorescence under Longwave (365nm LED) UV light: Blue