2-640-593 - © CM Dixon/Heritage Images

Calcite Formations, Hveravellir Hot Springs, North East of Langjokull, Iceland, 20th century. Hveravellir Hot Springs, a low temperature area at the northern edge of Kjalhraunnature lava field, a nature reserve on the Kjolur route between Langjokull and Hofsjokull. Calcite is a constituent of sedimentary rock, particularly limestone, much of which is formed from the shells of dead marine organisms.