Mesosiderites are stony-iron meteorites that are impact mixtures (breccias) composed of silicate minerals from a differentiated meteorite like a eucrite and FeNi metal from an iron meteorite. Most are the products of violent collisions between stony and iron asteroids. Mesosiderites are rare, only about 0.6% of all known meteorites.

One can find photos of mesosiderites on the internet. The ones below are particularly good as they are presented on the Meteorite Picture of the Day website. Note that the complex relationships between silicates and metal.

I have been sent photos of what I suspect are industrial slags that finders thought might be mesosiderites. If it is glassy and vesicular, then it is not a mesosiderite. The ultimate test is to determine the composition of the metal. Slags will not have metal with 5-30% Ni.