LEGO's Power Miners theme, launched in 2009, centers on a team of miners exploring underground caverns to investigate the cause of severe earthquakes. During their expedition, they discover energy-rich crystals and encounter various Rock Monsters. The miners aim to collect these crystals to prevent the monsters from consuming them and causing further seismic disturbances. Complementing the main sets, LEGO released key chains featuring characters from the Power Miners theme. Notable examples include the Boulderax Key Chain (set 852505) and the Meltrox Key Chain (set 852506), both introduced in 2009.
Summary
Gear Key Chains / Power Miners Green Rock Monster Key Chain set 852505 was released on February 23, 2009, retailing for $5, it has since been retired. New, unopened sets are valued at $8, while used sets sell around $6.
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