Polarised light micrograph of migmatite from Kesselalm, Proveis, South Tyrol, Italy. Migmatite is a highly metamorphic rock found in the Eastern Alps. It was formed from sedimentary rock such as shale or greywacke that experienced such high temperatures and pressures that its feldspar and quartz components partially melted. This metamorphosis took place 335-385 million years ago. Migmatite is composed of quartz, feldspar, garnet, kyanite, biotite, and light mica (muscovite). Magnification: x60 when printed at 15 centimetres wide.