Sericite schist
It is a metamorphic rock which is easily divided into thin plates (schist or slate flow) with a lustrous shine.
The schistosity surfaces are essentially formed by sericite which is a white mica in small shiny flakes.
The other minerals (quartz and plagioclase) are not visible to the naked eye. The slates used to cover roofs or formerly used by schoolchildren for writing with chalk are a variety of schist.
The schistosity surfaces are essentially formed by sericite which is a white mica in small shiny flakes.
The other minerals (quartz and plagioclase) are not visible to the naked eye. The slates used to cover roofs or formerly used by schoolchildren for writing with chalk are a variety of schist.