name: Hall of Gemstone
originalText: During each player's upkeep, that player chooses a color.\nUntil end of turn, each mana-producing land produces mana of the chosen color instead of its normal color.
printings: MIR, WC98
text: At the beginning of each player's upkeep, that player chooses a color. Until end of turn, lands tapped for mana produce mana of the chosen color instead of any other color.
type: World Enchantment