3654 Weeksite, Opal, Autunite No 8 Claim, Thomas Mountains, Juab Co, Utah, USA

There are two distinct species here based on the fluorescence response. Pale yellow fibrous sprays of weeksite that look like they fluoresce yellow, but are just reflecting the surrounding opal that fluoresce strongly. Width of view 11.5mm. Stack of 40 images (white light) and 10 images (UV).

Use the slider on the photo below to compare the white light and UV images. Click here for a higher resolution version.