CL spectra of a zircon grain containing a variety of rare earth elements (concentration 0.1 – 100 parts per million). Wavelength spectra were recorded with a MonoCL4™ detector and provided courtesy of Rolla Zanetti, Washington University in St. Louis, and the McDonnell Center for the Space Sciences.

Reservoir rock

The oil and gas industry frequently uses cathodoluminescence (CL) to characterize reservoir rocks.

Rare earth elements (REEs)

The last 20 years have seen an explosion in demand for REEs due to their use in rechargeable batteries, magnets, military-grade metal alloys, and many optoelectronic devices. Minable concentrations of REE-bearing minerals, such as apatite and monazite, are uncommon with sometimes restricted market availability.

CL can reveal the presence of, and identify, REE within a mineral. Their distribution(s) may be mapped even at concentrations lower than ten parts per million based on the distinct emission spectrum of each REE.


Porphyry deposits are one of the world's most important repositories of copper, gold, and molybdenum. High-resolution, scanning electron microscope CL mapping allows the detailed interpretation of the crystallization history within porphyry copper ore deposits to be understood.


Many gemstones, including diamond and corundum (sapphire or ruby), exhibit strong CL and are widely studied. The inhomogeneous internal structure can reflect changes that occur both during growth as well as post-crystallization. This allows, for example, natural and synthetic diamonds to be distinguished based on their spectrum and a detailed understanding of the various colors they exhibit.