Do the terms pebble, sand, and silt primarily describe the material's composition or its physical dimensions?

Answer

Their physical dimensions (shape and size)

The names pebble, sand, and silt describe shape and size, not what the material is made of; a pebble could be igneous, metamorphic, or sedimentary material.

Do the terms pebble, sand, and silt primarily describe the material's composition or its physical dimensions?
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