Cetraria islandica and is a lichen.

Iceland lichen, cetraria, fucus, muscus, and eryrngo-leaved (spiny-leaf) liverwort.

Rare possibility of allergic reaction. Risk of lead poisoning in poorly prepared Iceland moss. Excessive doses or prolonged use: gastric irritation and liver problems.

leaves

No not leaves, there are no native trees in Iceland. The answer is lichen, I kind of moss that grows on rocky outcroppings in arctic countries like Iceland

Calcium, iodine, potassium , phosphorous, and vitamins.