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After you get back from Cianwood, go to Jasmine and talk to her to challenge her in the gym battle.She uses the Steel type so Fire and Ground are two recommended types to fight her with, since both types of moves are super effective on her team.

From here, head to Cinawood Gym to battle Chuck.

[edit] Leader

• Leader Jasmine:
  • Magnemite (lvl. 30, 571 EXP)
  • Magnemite (lvl. 30, 571 EXP)
  • Steelix (lvl. 35, 1470 EXP)
  • 3500

After you defeat Jasmine, you'll receive the Mineral Badge and Iron Tail (TM 23).