Garnet in peridotite sample, close-up. This garnet (red) is in a sample of a rock called peridotite, from the Alpe Arami in the Alps. Peridotite is an igneous rock, formed from molten rock beneath the Earth's surface. It is one of the deepest rocks found on the Earth's surface, originating in the Earth's upper mantle. This sample was pushed up during the Alpine orogeny (the collision that formed the Alps). In some places in the rock, the garnet has been transformed into chlorite (green). This sample is from Ticino, Switzerland.