This sink definitely has a matte finish. Yes it is granite/quartz, and you may expect it to have a high gloss, polished finish like a granite/quartz countertop but it most certainly has a matte finish. The cracks you notice on the underside of the sink are contraction fissures. The sink is molded and cured upside down so that the quartz particulate drops due to gravity to the front face of the sink. This makes the top side of the sink the hardest and most durable surface possible. As the material cures it draws away from mold on the back side of the sink, resulting in a surface that is not perfect like the front side. Little rough patches or small "cracks" are normal and in no way diminish the strength of the sink.