Slate is heavy, often dark colored and smooth
when it breaks in sheets. It does not contain visible minerals, but with
a microscope, you would see that all its minerals are lined up. The
properties of slate make it ideal to use on the top of pool tables,
shingles on roofs, walking stones, and the original blackboards, which
teachers write on.
Phyllite resembles slate but has a somewhat
coarser texture. The flat surfaces have a lustrous sheen due to mica and
chlorite. However, it is not as hard or flat as slate, and not used in
construction like slate.
Slate outcrops in Grand Canyon