flowstone

Flowstone is a cave deposit formed by mineral-rich water flowing over surfaces, typically calcite in limestone caves. As groundwater rich in dissolved calcium carbonate moves along walls, ceilings, or floors, it degasses carbon dioxide into the cave air, causing calcium carbonate to precipitate and build up coatings and layers. Over time, continuous flow creates broad sheets and curtains that can cover large areas, often with a glossy or translucent appearance. Impurities such as iron, copper, or manganese can tint flowstone in colors ranging from red and orange to green or black.

Flowstone occurs in many karst regions around the world and can take several forms. Sheet flowstone grows as smooth sheets on walls or floors, while draperies or curtains form along inclined surfaces. Cascading flowstone can develop where water runs over steps or shelves. Growth rates are generally slow, typically millimeters per year, though more rapid deposition can occur near waterfalls or in areas with abundant flow. The resulting formations often show layering and banding that reflect changes in water chemistry and flow over time.

In cave science and conservation, flowstone is valued for both its beauty and its geological record of past hydrological conditions. It is highly susceptible to damage from physical contact, vibrations, and alterations to cave airflow or water supply, and is commonly protected in national parks, show caves, and other managed sites.