Gem Mine9

"Gem Mines access a rare deposit of this highly valuable resource! Mining gems is slow and hard work."

Gem Mine Ruin Gem Mine1 Gem Mine2 Gem Mine3 Gem Mine4
Ruin Level 1 Level 2 Level 3 Level 4
Gem Mine5 Gem Mine6 Gem Mine7 Gem Mine8 Gem Mine9
Level 5 Level 6 Level 7 Level 8 Level 9

  • Summary
    • The Gem Mine can be unlocked in the Builder Base. It requires Builder Hall 3 to be repaired.
    • The Gem Mine, as its name suggests, produces gems, albeit very slowly. These mined Gems are then stored until the player collects them or the storage fills.

  • Upgrade Differences
    • Gem Mines undergo a significant visual change at levels 3, 8 and 9.
      • In its initial ruined state, it appears as a derelict, overgrown cave. A Gem insignia on a wooden hexagon on the side of the rocks can be found on the Mine's side. There are large broken wooden planks covering the entrance, and a broken box. There are also Gems scattered around the Mine.
      • When reconstructed, the Gem Mine is a cave-like structure with a wooden arch supported by ropes at the entrance. The Gem insignia is present on the side of the Mine, and a rail conveyor extends out of the cave, into a box containing Gems. Outside the cave is a torch.
      • At level 2, the Gem Mine's arch and base is reinforced by metal.The grass on the side of the Gem Mine has disappeared.
      • At level 3, the top of the cave is replaced by an open roof and a pulley system. More wooden planks are added to the sides of the opened roof, in order to support the pulley. Additional reinforcing metal plates appear at the top of the entrance.
      • At level 4, the reinforcing metal plates change to a bronze-colored scheme. A second pulley is also added.
      • At level 5, the reinforcing wooden structure now extends to the back of the cave, and additional bronze plates are added to the back side of the roof.
      • At level 6, the pulley system becomes bronze, with wood covering the roof.
      • At level 7, a bar is fixed to the roof, and it now suspends the pulley system. Ropes can be seen between the two pulleys, and the roof now appears to be made of stone.
      • At level 8, the wooden supports at the corners are replaced with larger wooden beams. The beams are slanted and support a new pulley system consisting of one large pulley with its bar attached to the roof by bolts.
      • At level 9, the bases of the supports at the corners have been replaced with iron bases, and the pulley system on top has been replaced with a larger one.

  • Defensive Strategy
    • This building serves no purpose on defense, so placing it on the outside to protect your defenses can be good.
    • Placing it in the corner can stall your opponent from getting three stars on your base.
    • This building has low hitpoints, so it is better to place it outside of the walls or the base.

  • Trivia
    • The Gem Mine is the only building that produces Gems.
    • There are no storages for the Gems except for the Gem Mine due to your unlimited Gem inventory.
    • Unlike the Gold Mine, there is no cart that delivers the Gems to the surface. Instead, a conveyor belt delivers the Gems to the surface and deposits them into the box at the entrance.
    • When the Gem Mine is full, the Gems are in a large, unorganized pile right outside the entrance of the Gem Mine.
    • At level 8, to get the worth of a bundle; it takes 16 days to get 80 Gems and up to a staggering 7 years to get 14,000 Gems.

  • Icon Descriptions
    Icon InfoTapping this icon displays information about the Gem Mine, such as Level, Capacity, Production and Hitpoints.
    Icon UpgradeTapping this icon begins upgrading the Gem Mine to the next level, if you have enough resources and a free Master Builder or O.T.T.O. When the Gem Mine is at maximum level, this icon is not shown.
    Icon HoBTapping this icon instantly upgrades the Gem Mine to the next level, at the cost of one Hammer of Building if you have one. When the Gem Mine is at maximum level, this icon is not shown.
    Icon FinishNowTapping this icon, which is displayed only while an upgrade is in progress, instantly finishes that upgrade at the cost of the displayed number of Gems.
    Icon FinishNowBoBTapping this icon, which is displayed only while an upgrade is in progress, instantly finishes that upgrade at the cost of one Book of Building. This icon is only shown if you have at least one Book of Building.
    Icon FinishNowBoETapping this icon, which is displayed only while an upgrade is in progress, instantly finishes that upgrade at the cost of one Book of Everything. This icon is only shown if you have at least one Book of Everything but do not have a Book of Building.
    Icon CancelTapping this icon, which is displayed only while an upgrade is in progress, cancels the current upgrade and refunds half of the upgrade cost.
Builder Hall Level 1 2 3 4 5 6 7 8 9
Number Available 0 0 1 1 1 1 1 1 1
Size Size
Build Cost
Build Time
Experience Gained
Production Rate (per day)*
Production Time per Gem
Time to Fill
Catch-up Point** Hitpoints
Builder Hall Level Required
Builder Hall9
1 120,000 1h 60 10 2.16 11h 6m 40s 4d 15h 6m 40s N/A 300 3
2 180,000 2h 84 11 2.40 10h 4d 14h 18h 345 3
3 240,000 6h 146 12 2.64 9h 5m 27s 4d 13h 5m 27s 2d 12h 397 3
4 450,000 8h 169 13 2.88 8h 20m 4d 12h 20m 3d 16h 457 4
5 1,000,000 10h 189 14 3.12 7h 41m 32s 4d 11h 41m 32s 5d 526 5
6 1,500,000 12h 207 16 3.36 7h 8m 34s 4d 18h 17m 9s 6d 12h 605 6
7 2,500,000 1d 293 18 3.84 6h 15m 4d 16h 30m 7d 696 7
8 3,500,000 2d 415 20 4.32 5h 33m 20s 4d 15h 6m 40s 16d 800 8
9 4,500,000 3d 509 22 4.80 5h 4d 14h 27d 840 9

* These values are exact values that are derived from the game files. In-game, this statistic is rounded down to one decimal place.

** The Catch-Up Point is the time at which the newly upgraded Gem Mine has equaled the total production of the mine had it not been upgraded - this does not consider recovering the cost of the Builder Elixir required to perform the upgrade.

Caveat: The Catch-Up Point calculation assumes that the player collects all resources from the Gem Mine without allowing it to reach its storage capacity, as resource production ceases at that point. If the player is unable to regularly collect and achieve the full potential of the collector, the Catch-Up Point is actually shorter and performing the upgrade becomes more advantageous.

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