A dark halo crater is a crater, which is some cases may be volcanic in origin, that is surrounded by an ejecta blanket darker than the adjacent landscape.

This small crater left of center in the image shown here is located near Mare Tranquillitatis, 200 meters north of Censorinus A crater. The surrounding area is covered by ejecta coming from Censorinus, which is about 12 kilometers distant (the surface streaks point back to the crater). The dark and bright areas are intermixed, and the tiny dark ejecta crater is located on the brighter portion of the ejecta. The brighter ray materials are likely on the top of darker materials, which are perhaps simply mature soils or maybe impact melt from the earlier Censorinus impact event. So when the small crater was formed, it excavated dark material from beneath a bright ray.