Coralline Algae / Maerl

Physical Properties

Hardness: 3 (Mohs scale), Color: Pink to deep purple (living) to bleached white (dead), Luster: Dull/Earthy, Structure: Branching or modular calcified nodules, Cleavage: None

Formation & Geological History

Formed through the biological calcification of red algae (Rhodophyta) in marine environments. These specimens grow over decades or centuries in shallow sunlit waters, forming 'maerl beds.'

Uses & Applications

Used as a soil conditioner (lime), in water filtration systems, as a source of calcium supplements, and in marine conservation efforts.

Geological Facts

Maerl beds are considered 'blue carbon' sinks, sequestering significant amounts of CO2. They are often protected marine habitats as they support high biodiversity.

Field Identification & Locations

Identify by its unique 'popcorn' or branching texture and vibrant purple/pink hue. Commonly found washed up on Atlantic beaches in Ireland, Scotland, and Brittany.

Identified on: 4/18/2026

Mode: Standard