sort of
Any fine grained rock, in the abscence of other fractures, will tend to break along a curved surface. However, a true conchoidal fracture actually looks like the ridges on a shell, or the way the fractures on a chipped arrowhead look. (http://en.wikipedia.org/wiki/Conchoidal_fracture)
The shape of many of the cobble and smaller size rocks on the surface of mars are called ventifacts (http://en.wikipedia.org/wiki/Ventifact), semi-triangular shaped rocks that have been polished by the saltation of sand grains driven by the wind. Such shapes are common here on terra, and we saw lots via the Spirit rover.