That means we can identify minerals using how they appear in doubly polarized light under a microscope ... the crystals formed. Plagioclase feldspar from Edison Butte rhyolite seen at 40x in doubly ...

That means there are five ways to rotate the crystal around an axis so that it looks the same. “Fivefold symmetry is very rare ... rotate the crystal under the microscope and show that it ...

However, the people who study how these rocks form take it at least one step further and that is looking at rocks under the microscope ... what it sounds like: very thin slices of rock, usually ...