Go through our collection of Pebble Stones made from agate at Hanifa Crystals. A pebble is a clast of rock with a particle size of 4 to 64 millimetres based on the Krumbein phi scale of sedimentology. Pebbles are generally considered larger than granules (2 to 4 millimetres diameter) and smaller than cobbles (64 to 256 millimetres diameter). Generally, sedimentary rock is fairly soft and may break apart or crumble easily. You can often see sand, pebbles, or stones in the rock, and it is usually the only type that contains fossils. Examples of this rock type include conglomerate and limestone. Pebbles are all the same things: rock material. The main difference is size. Stone is generally used for large amounts, rock is just the generic term, boulders are pieces of rock bigger than a foot across or so, and pebbles are smaller than 2.5 inches - roughly. Choose from varieties of tumbled stone available online and place an order today!