Global Volcanism Program | Image GVP-10097
Basaltic scoriae blocks from the Hoya Estrada maar have light-colored silicic rims. This results from large scale mixing of basaltic magmas with silicic end members leaving remnants of the light-colored silicic magma on the outside of the blocks after deposition. Coin provides scale.
Photo by Jim Luhr, 2002 (Smithsonian Institution).