Through weathering, typically from abrasion or tumbling.
it depends on how it actually breaks
Through weathering, typically from abrasion or tumbling.
The shape of a rock that has just broken off a larger block of rock is either amorphous or jagged. It will eventually undergo weathering and become smooth.
A smooth, black rock is likely to be basalt. Basalt is an extrusive igneous rock that is commonly dark in color and has a fine-grained texture, giving it a smooth appearance.
Rocks become smooth through the process of weathering, which includes abrasion from wind, water, or ice over time. Rocks that are not smooth may have experienced less weathering or may be composed of harder materials that resist erosion. The smoothness of a rock can also depend on its location, as rocks in a riverbed or along a coastline are more likely to become smooth.
some from weathering
obsidian
Yes, it is.
Sure, a boulder is a large rock.
Pavement or smooth rock runoff affects waterways because they create more impervious surfaces.
Metamorphic rock can be coarse grained or fine grained.
Shale