If you slide the rocks from Earth’s crust to half the width of a hair you can shine light through them and can see the insides better. Thanks for the Sedgwick Museum of Earth Sciences we can see, in the images from above, the beauty of those thin sections of igneous rock photographed under a polarising microscope.
In Cambridge University’s article called Magma arta we can read that studying the crystal structure of rocks will help us understand better how Earth works. The focus is on igneous rocks, which are frozen remains of magma formed at depths of 100 km or more from the mantle and then spewed out of volcanoes.
Many regard volcanoes as perilous “creatures”, but they are, in a certain way, the messengers of Earth because the magma they spew out might contain more clues as to how the mantle works and what could we encounter in Earth’s depths.
Some more info:
The collection of igneous rocks, housed at the University of Cambridge’s Sedgwick Museum of Earth Sciences, dates back to at least the early 1800s and contains around 160,000 rocks and about 250,000 slide-mounted rock slices that are thin enough to let light through.
via Cambridge University.