Some substitutes for fleur de sel include flaky sea salts such as Maldon from England or Marlborough sea salts from New Zealand. Other substitutes are tamise de Guerande and sel gris de Guerande. Like fleur de sel, these are French sea salts.
Tamise is harvested from the same salt ponds as fleur de sel, but is prized for its moistness, coarse finish and pleasing gray color. It is used as a finishing salt, though sel gris de Guerande is used as a cooking salt. This salt comes in both fine and coarse grain. Fine grain sel gris de Guerande is lower in sodium than regular table salt.
Maldon sea salt is produced exclusively by the Maldon Crystal Salt Company in England and has been since 1882. It has no additives and contains only those minerals found in the sea from which it comes. It is known for its delicate, pyramidal crystals that crumble easily, and it has a mild taste that reminds the diner of the sea.
Marlborough sea salt comes from seas off the province of the same name, which is found at the north end of New Zealand's South Island. It has soft, flaky crystals, a delicate taste and a tendency to stick to foods. Like Maldon salt, it is easy to crumble between the fingers.