Microgabbro on Carrock Fell

 

This feature is on the Mosedale flank of Round Knott, just below the summit. It turned out that the bands in the rock were tiny - see foot in photograph for scale. I hadn't figured that the picture in the book we were using had a pencil in the photograph, not a pole!! It's this one if you're interested. The big trick here is the differential precipitation and settling of different minerals. The book says that augite with iron and magnesium precipitated first and settled, leaving a mixture heavy in calcium and aluminium (plagioclase) so this then precipitated, until the original balance was restored and then the process repeated forming the bands.