The Crust the Crust Game Slag — Wiki & Guide

The Crust's economy runs on 21 resources processed from 10 raw mined materials (per the Kickstarter fact sheet). The two that confuse new players most — because one piles up as waste and the other hides in walls — are slag and rare earth minerals. Here's the full picture.

The full resource table

Stage	Resources
Mining (raw)	Regolith, Water Ice, Iron Oxide, Titanium Oxide, Silicon Oxide, Aluminum Oxide, Rare Earth Minerals, Slag, Helium-3, Argon, Methane, Neon
Ore processing	Steel, Silicon, Titanium, Aluminum
Early/mid production	Smart Concrete, Titanium Plates, Rare Earth Elements, Components, Microcircuits, Carbon Fiber, Fuel, Modular Terminals

Raw oxides come out of extractors on underground veins (iron, titanium, silicon, aluminum) or surface deposits; gases (argon, methane, neon) are pumped on the surface; regolith is everywhere. The processing flow is linear: oxide → smelter → refined metal → plates/components/microcircuits, with regolith pressing into Smart Concrete along the way.

Slag: the byproduct with three uses

Slag is left behind by the Single and Multi-Regolith Refineries — the wiki lists both as its only source — and it accumulates fast. What the community actually does with it:

1. Smart Concrete. The Smart Concrete Factory consumes slag plus silicon — the forum's consensus answer to "what to do with all this slag": "making smart concrete with it is an easy and lucrative way to get rid of it." Creator runs agree; Pravus's conclusion after building one: "Now we have a use for all that slag. That's going to help a lot."
2. Farm organics. Farms use slag to grow organics — "but not at any rate that will let you get rid of it," as one player measured it. Treat it as a sink, not a solution.
3. Sell it by contract. Contracts to sell slag appear periodically — check the contract board before treating it as pure waste.

If you still have surplus: bulk storage accepts slag — roughly 9,000 units per storage by community measurement. There is no dumping ground or disposal mechanic, and a player sitting on "around 200k surplus slag" called it "annoying" — so build the concrete factory before the mountain builds itself. (It's also worth remembering slag is evidence of a healthy refinery line — the EP12 outpost-era streamer treated full slag buckets as a logistics todo, not a crisis.)

Rare Earth Minerals: two ways to mine them

Rare Earth Minerals (REM) are the economy's luxury good — Rare Earth Elements sell for a "pretty hefty chunk," and plates made from them are the classic money-maker (sell in 100-lots above ~600 credits, per the forum's standing advice). Getting them:

• Underground nodes. REM appears as glowing nodes in underground rock walls. Drones clear the nodes and haul the minerals to bulk storage, which feeds the Rare Elements processing line. No extractor required.
• Surface MDR mining. Once you reach the Mobile Drilling Rig (MDR) quest milestone, a working MDR mines surface deposits of every mineral — aluminum, iron, silicon, titanium and REM. The support chain matters: a Cargo Truck services the MDR, a Cargo Dock receives its regolith, and Rover geological survey research lets you actually see where deposits are ("at first you may be mining blind" without it). One player who delayed that quest described spiraling into "spaghetti land" underground and eventually restarting — the MDR milestone is the intended unlock for surface mining at scale.

Helium-3, gases and the rest

Helium-3 deserves its own page — it's the late-game outpost resource behind the fusion economy: see Helium-3. The atmospheric gases (argon, methane, neon) feed alternative production recipes and fuel; they're covered in the recipes guide. Water Ice is the life-support feedstock (see colonists), and plain regolith is your construction backbone via the pressing line.

Quick answers

• What do I do with slag? Build a Smart Concrete Factory (slag + silicon), route surplus into bulk storage (~9,000 each), sell it when a slag contract appears, and let farms sip the rest.
• How do I get rare earth minerals? Drone-clear the underground REM nodes first; then unlock the MDR quest for surface-scale mining with truck + cargo dock support.
• What's worth selling? Rare Earth plates above ~600 credits per unit, and whatever a contract specifically asks for — never the raw oxides when a refined good will do.