Also known as Irish moss, this purple-tinged, frond-like plant is found growing abundantly along the rocky Atlantic coastline of Europe and North America. In its fresh condition it is soft, varying in colour from a green-yellow to a dark purple. It may also be dried to a translucent creamy white horn-like consistency.

Carrageen is an important source of agar-agar, a vegetable gelatine used as a thickener and stabiliser in the food industry. A nourishing jelly may be made by simmering the moss in milk or water until most of it dissolves, then straining and leaving it to set. Vanilla may be added to mask the faint taste of the sea.