Polished Rocks

Some fine-grained-crystalline earth rocks can be rounded and polished by abrasion (e.g., on a sandy beach) to the point where the surfaces become shiny and resemble meteorite fusion crusts. Most such rocks are dark basalts. The shiny surface is not a “crust,” however. When broken the unpolished interior is the same color as the exterior, unlike in a meteorite.

These rocks do not have fusion crusts. If broken in two, the inside color would be the same as the outside color.