Quartz - Cave-In-Rock, Illinois
Contributed by: Chris Clemens
Date: Apr 30th, 2026
Locality: Cave-in-Rock, Cave-In-Rock Mining Sub-District, Hardin County, Illinois, USA (See on Mindat)
Size: 64 x 37 x 76 mm
Weight: 184 g
Description:
The Cave-In-Rock area of Hardin County, Illinois, is best known to collectors for its historical production of world-class specimens of fluorite. However, the mines of that area produced many other minerals as well, some of which are fluorescent. This is a specimen of quartz crystals from Cave-In-Rock that shows an interesting fluorescent response under both shortwave and longwave UV due to the presence of hydrocarbon, and other organic, activators.
Originally posted by Chris Clemens on Nature's Rainbows in 2017.
Summary of luminescence responses:
Quartz (Mindat) (RRUFF)
- Fluorescence under Longwave (365nm LED) UV light: Yellow
- Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Yellow