were mined. Poland emerged as an important producer during the 1970s after the discovery of copper deposits that were rich in silver, before the centre of production returned to the Americas the following decade. Today, Peru and Mexico are still among the primary silver producers, but the distribution of silver production around the world is quite balanced and about one-fifth of the silver supply comes from recycling instead of new production. Symbolic role Silver plays a certain role in mythology and has found various usage as a metaphor and in folklore. The Greek poet Hesiod's Works and Days (lines 109–201) lists different ages of man named after metals like gold, silver, bronze and iron to account for successive ages of humanity. Ovid's Metamorphoses contains another retelling of the story, containing an illustration of silver's metaphorical use of signifying the second-best in a series, better than bronze but worse than gold: In folklore, silver was commonly thought to have mystic powers: for example, a bullet cast from silver is often supposed in such folklore the only weapon that is effective against a werewolf, witch, or other monsters. From this the idiom of a silver bullet developed into figuratively referring to any simple solution with very high effectiveness or almost miraculous results, as in the widely discussed software engineering paper No Silver Bullet. Other powers attributed to silver include detection of poison and facilitation of passage into the mythical realm of fairies. Silver production has also inspired figurative language. Clear references to cupellation occur throughout the Old Testament of the Bible, such as in Jeremiah's rebuke to Judah: "The bellows are burned, the lead is consumed of the fire; the founder melteth in vain: for the wicked are not plucked away. Reprobate silver shall men call them, because the Lord hath rejected them." (Jeremiah 6:19–20) Jeremiah was also aware of sheet silver, exemplifying the malleability and ductility of the metal: "Silver spread into plates is brought from Tarshish, and gold from Uphaz, the work of the workman, and of the hands of the founder: blue and purple is their clothing: they are all the work of cunning men." (Jeremiah 10:9) Silver also has more negative cultural meanings: the idiom thirty pieces of silver, referring to a reward for betrayal, references the bribe Judas Iscariot is said in the New Testament to have taken from Jewish leaders in Jerusalem to turn Jesus of