It is not scratched by a knife and breaks along irregular surfaces. Marine sediments deposited during regres-sion get coarser in size as you move vertically upward through the pile. It is due to compression and results in crustal shortening. Often a graben forms along the rift. Commonly, schists include quartz, feldspars, and micas, but mineral compo-sition is not an essential factor in its definition.
Shales break easily along their layering, especially along weathered surfaces.
They feel smooth to the touch, not gritty. The tip of the funnel shape points in the direction of the location of energy release. Usually several cones form, nested within one another like stacked soup bowls with sharply pointed bottoms. They feel grittier than shales or mudstones. Mineral grains re-grow in the solid in parallel fashion so that the resulting slate breaks along flat, smooth, usually reflective surfaces.