The Quarrytop Mine is the game's only true multi-floor dungeon, and the Harvest Moon: Echoes of Teradea mine floors are earned through the mining union rather than found. Floors are earned in order: 10, then 30, then 50.

Harvest Moon: Echoes of Teradea mine floors and how to get in

StepWhat it costs
1Bring 3 Apple, 6 Wheat and 6 Rye to Lorelei in the southeast corner of Quarrytop — the union leader accepts the "bribe" and grants access down to Floor 10
2Buy an Ore Bag from Travis at the counter — Small holds 5 varieties, Regular 15, Large 30
3Work the floors down

There is no entry fee for the mine itself, but the guild will not let you past the first floor until you buy the Ore Bag. If your bag is too small, anything that does not fit is left on the ground.

The Quarrytop mining union: Lorelei, in a white coat with lavender shoulder pieces and a gold necklace, gestures while the dialogue box reads 'In order to protect the mine's resources, you'll have to follow the union's rules. Understood?'
Lorelei sets the union's terms before the mine floors open.

Where the bribe materials come from

Wild apples are in the Brown Bear Territory, Wheat Seeds are sold at Richard's store in Bloomfield, and Rye Seeds cost 15 G each at Heather's General Store in Quarrytop.

The Ore Bag matters more than it looks: without one you cannot pass Floor 1, and with a Small Bag you will leave most of a floor's haul on the ground. Buy the Regular or Large bag before you go deep.

What each floor range holds

FloorsContents
1 to 4Stone, Iron Ore, Raw Glass Gemstone, Raw Agate Gemstone
5A Mining Union Card lying on the ground
6 to 9Add Bronze Ore and Raw Jade Gemstone
10The limit of Lorelei's temporary permission
11 and upCrystal
12 and upRaw Crystal Gemstone, which Doc Jr. needs for the Mist-Dispelling Lantern
21 and upGarnet
26 and upAmethyst
31 to 50Unlocked by the mining union ID upgrade

The Floor 5 Mining Union Card is the pivot: Glenn asks you to keep it, and it gives you unrestricted access to the mine. The materials themselves, and which tier of node they sit in, are on the ore and gems page.

Step 3: work the floors down

The mine entrance is the smaller door with wooden beams in the middle of the entrance area. Dig up rocks and ore nodes until you find the ladder leading down to the next floor — the early floors are easy to get through.

When you come back up, turn the Ore Bag in to Travis, and you earn Happilia from the turn-in as well as from requests and gifts, which is what fills the Quarrytop Happilia bottle for the Spirit Tree.

The two union upgrades come from Travis: 5 Agate, 5 Jade and 5 Bronze for the guild membership permit, which grants access down to Floor 30, and then 10 Crystal, 10 Amethyst and 10 Garnet for the mining union ID, which opens Floors 31 to 50. The wider dungeon map is on the dungeons page.

The King's Chamber

There is also a King's Chamber at the end of the mine corridor, behind large red doors. That is where you meet Gorgon, the King of the Underworld, and find the withered Quarrytop Spirit Tree.

Restoring that tree with a full bottle of Happilia triggers the Quarrytop Spirit Tree Hyperbloom, which temporarily increases the number of ore nodes in the mine — the one time in the game when the mine gives you more rather than less. It is the strongest argument for rushing the Quarrytop chapter rather than farming it slowly. The four trees are on the spirit trees page.