There are various ways to classify rocks. One simple method is based on the manner in which the rocks formed. Attached is the answer key that is associated with the EdGEO teacher workshop delivered by Mining Matters at the Canadian Ecology Centre July 29 - August 2, 2013. The three rock groups are fondly referred to as: Baked and Squeezed (metamorphic) Explosive Magma (Igneous) Layered Clasts (Sedimentary)