Ruby in Fuchsite tumblestones

Corundum, (sapphire and ruby) forms deep in the Earth’s crust and is brought to the surface in igneous rocks that are high in aluminium but low in silicon, such as basalts. Corundum is also found in rocks that have been metamorphosed. Fuchsite is a green variety of muscovite mica. Chromium is the source of its green color. Fuchsite is found in phyllites and schists in metamorphic rocks of the greenschist facies.