Check the listing for details. Gneiss, a type of Metamorphic Rock. Condition: Used. Listed at 13.20 USD. Gneiss is a type of metamorphic rock that is created through the process of heat and pressure acting on existing rock formations. This process alters the mineral composition and structure of the rock, resulting in a unique and visually appealing material that is highly sought after by collectors and enthusiasts. With its intricate layering and variation in color, gneiss makes for a striking display piece or a versatile addition to any collection of rocks, fossils, and minerals.