유문암, or Yumunam, is a type of volcanic rock formed from the rapid cooling of lava. It is characterized by its fine-grained texture and often contains small gas bubbles, giving it a unique appearance. This rock is typically found in areas with past volcanic activity. The formation of 유문암 occurs when lava erupts and cools quickly, preventing large crystals from developing. It is commonly used in construction and landscaping due to its durability and aesthetic appeal. Additionally, 유문암 can provide insights into the geological history of an area, helping scientists understand past volcanic events.