Polarised light micrograph of a thin section of basaltic dyke. The larger crystals are the minerals clinopyroxene and olivine, which are sitting in a finer grained matrix of plagioclase. This sample was collected from Straumsvola Mountain, Antarctica, and dates to the Jurassic Period (201 to 145 million years ago). It has been calculated that the crystallisation temperature for the magma that formed this rock was around 1,300 degrees Celsius, indicating elevated mantle temperatures in the Antarctic at this time.