This is not seaweed but a kind of calcified cold water coral and coralline algaehaving the Latin name of Lithothamnion calcareum.
It is dredged from the sea off the French and English coasts. It has been used by Cornish farmers since before c1650
In Northen France, it is called maerle and is used by Breton garlic, onion and broccoli farmers to improve their crops.
Calcified seaweed consists of about 50% calcium, 5-10% magnesium carbonate and a wide range of beneficial trace elements Zinc, Copper, Sulpher ,Iron,Manganese, Cobalt , Boron, which may be Continue reading