Mesosiderite meteorites are stony irons with roughly 50-50 proportions of each. The iron is asteroidal core and the stone is the crust of a differentiated asteroid. Mantle material is rare. Several formation scenarios have been proposed and scientists continue to discuss the matter. Mesosiderites are classified by mineralogy and texture. Estherville is an A3/4. That is, plagioclase content of the stony portion is greater than 25% (volume) with much of the remainder calcium-poor pyroxene. The matrix is a highly recrystallized melt breccia.