Every crystal you can carry has two confirmed uses: sell it for Cash, or place it in the garden for digging luck. A third prompt, crystal upgrade, appeared in one playthrough. Its costs and results are not published, so read that card in game before you spend.
Weight and price
Crystals are weighed in kilograms. Promotional images show finds marked 96.4 kg and 98.4 kg. Weight is what the backpack spends. Price is a separate number on the crystal.
They do not move together. In one recorded haul, a 9.6 kg crystal was priced around 6,000 Cash, while other heavier pieces were worth less per kilogram, and some crystals were too heavy to pick up at all. A 54 kg crystal stayed on the ground after a small backpack upgrade. There is no official Cash-per-kilogram table. Use the number on the crystal you are holding.
Sell
- Fill the bag or hit the cold limit.
- Return to base.
- Sell at the selling point. Guides call this stall the Gem Buyer.
- Confirm the Cash total went up.
Nothing official says crystals sell themselves when the hour changes. Sell before you log off and before you want an empty bag for a new zone. A Backpack Full notice means you cannot pick up more until you sell or drop weight.
An early backpack step in one session cost about 20,000 Cash and the player was pushing capacity around 30 kg. That is one card on one save, not a price list. Read Carry More in the upgrade menu.
Garden
The description says placing crystals in the garden gives more digging luck. It does not say the garden pays Cash, and it does not say how much luck one crystal adds.
- Keep a spare you do not need for the next upgrade.
- Place it in the garden layout at base.
- Assume you may not get it back. No remove control is documented.
- Sell the rest.
Do not garden the whole run if you are stuck on a warmth, pickaxe, or backpack card. Luck does not pay the shop. Also do not expect a named crystal to guarantee a rarer find. The description does not publish that kind of percentage.
Settings are reported to include a Crystal Filter that can stop Common, Uncommon, and Rare drops from filling the bag. Turn that on only after those grades are no longer the Cash you need.