Getting into the mine
The Dinkum mines are a separate progression step from gathering ore on the surface. KRAFTON's old-keys FAQ says to obtain a Deep Mining Licence and construct the mine. That is the confirmed access route; a precise construction cost is not provided by the cited answer.
The publisher's broader description lists hidden mines alongside forests and red desert. Go in with the licence and the mine actually built on your island, not on the assumption that a surface rock automatically opens a lower floor. The order and cost of every mining upgrade are 待确认.
Old keys and useful materials
Keep old keys if you plan to visit the mine: the official FAQ explicitly connects them to the underground area. It does not provide a complete locked-room map or key-per-run budget. Check the current in-game interaction instead of following an unsupported guaranteed-reward route.
The 2026 Great Bite update also names Old Bowser, a rare material that can be found on all floors of the Mine. That item is used in the Servo's crafting path, according to the same patch note. "Rare" is not a published probability, so do not translate it into a numerical drop rate.
Multiplayer elevator permissions
KRAFTON's multiplayer FAQ says only the host can activate the Deep Mines elevator, with everyone inside. The FAQ also assigns building placement and town quest progression to the host. Co-op partners can still carry their own inventory to and from another island, but money is not pooled automatically.
The 1.0 patch refined several visitor permissions for containers, pickups and island edits. Coordinate with the host before a group trip and check current permissions rather than assuming every guest has full build access. No official material here promises that players can enter the mine on separate schedules in the same session.
What a drop guide cannot promise
The reviewed primary sources confirm mine access, old keys, the co-op elevator rule and one newer material. They do not supply a complete enemy table, floor-by-floor spawn map, or exact loot odds. Those figures are 待确认, even when a community video gives confident numbers.
Use this page as the route to the confirmed systems, then compare the live game's menus and the official patch notes for version-specific changes. Avoid selling old keys because a generic item list calls them junk. For a larger progression overview, the licence article separates skill gates from mine access.
QUESTIONS
What players ask
Should I sell old keys?
KRAFTON says they are needed for the mine, so keep them until you know what you need inside.