Hall of Gemstone (MIR) (#221)

Name: Hall of Gemstone
Mana Cost: {1}{G}{G}
Type: World Enchantment
Collector Number: 221
Oracle 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.
Rarity: rare
Artist: David A. Cherry