Mica schist with porphyroblasts of garnet, staurolite and kyanite. 2. Graphite schist. Slate is a fine-grained rock with well-developed slaty cleavage. Phyllite is .Mica-schist is a rock composed essentially of quartz and mica, usually either The mica plates all lie with their cleavage planes parallel to each other and give of feldspar grains among those of quartz, which are difficult to detect without the .