These techniques of setting stone against stone in a thick mosaic are related yet different. They are most often seen in Navajo stone work. Both methods require that each stone be rounded or beveled along its edges before being placed in the desired pattern.
Here is where the differences appear. Corn row refers to similar size pieces of stone set parallel, side by side in a neat row – the edges of each stone are usually rounded. Cobblestone refers to pieces that are fitted perpendicular or angled to each other like you’d see in a stone courtyard. Often cobblestone pieces vary in size and have beveled rather than rounded edges.
You can easily see why cobblestone inlay is called that if you’ve ever seen a cobblestone street in an old historic section of a US city or abroad. Besides cutting the stones so that they fit into an intricate pattern, the artist must also bevel each stone on every edge. This requires great skill and time and investment in materials.
A similar inlay pattern called cornrow has the stone pieces all laid parallel, like corn kernels on a cob.