This type of ventifact forms in arid, desert environments where prevailing winds blast loose sand against surface rocks. The constant abrasion grinds flat facets into the stone, and when the wind direction shifts or the stone flips, a second facet is carved. The intersection of these two polished surfaces creates a distinct sharp ridge.
Heard on the job
We found a perfect basalt zweikanter sitting on the desert pavement, showing exactly where the seasonal winds cut across it.
Insider tip
The name comes directly from German, meaning two edges. If a third face is cut, it becomes a dreikanter.