Iron was the material traditionally used for Sparta’s distinctive currency bars.
Ancient writers describe Sparta as using heavy iron spits or bars rather than the more valuable silver and gold coinage common elsewhere in the Greek world. The tradition is associated with Lycurgan reforms and with an attempt to discourage luxury, hoarding, and long-distance commercial activity. Because iron bars were bulky and inconvenient, they were thought to make large private fortunes and imported luxuries more difficult to manage.
The account is best understood as part of the ancient literary picture of Spartan austerity. Scholars debate how widely such iron money was actually used and whether the system was ever fully implemented in the idealized form described by later authors.
Sparta was not economically isolated. Its communities farmed, traded, produced goods, and interacted with neighboring regions. The iron-money tradition therefore does not mean that every transaction in Spartan territory used only bars. It reflects a famous reform associated with the city’s reputation for rejecting conspicuous wealth.