The rocks in Plantaberget are the same as in the other table mountains (basement, sandstone, alum shale, limestone, clay shale, and dolerite), but the mountain is part of the same limestone plateau as Varvsberget and Gerumsberget. The actual visible mountain thus consists only of clay shale and dolerite. Plantaberget’s dolerite plateau covers more than four square kilometres. Another name for Plantaberget is Högstenaberget. Its highest point is at 305 metres above sea level.