Some minerals can glow under certain conditions and there are ways to see that glow. The most popular way is to use ultra violet light of different wavelengths to induce the mineral to "fluoresce". This means the UV light acts with the mineral compounds to produce a third element, in this case light. There are hundreds of different mineral types that fluoresce and a variety of amazing colours. It is such a fascinating twist to rock collecting.
Many Precious and semi precious gems can also glow, such as Ruby and Diamond. The equipment to view glowing rocks can be a bit expensive, but new technologies are emerging at the moment that will soon make it very affordable to display your glowing treasures!
Below are some good websites to learn lots more about this little known but fascinating activity.