The tin ore which was first obtained from newly opened mines, used to be smelted and poured into moulds to make a pair of ingots shaped like the shell of a tortoise. This practice was associated with casting spells and was a substitute for sacrificing animals. In time, these ingots came to be used as money and their value was even higher than that of their tin content. The currency denomination of these ingots was based on the amount of tin that could be exchanged for one Spanish silver dollar (8 reales).
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