Caesium

Caesium adds a hidden ore to Factorio 2.1. Pegmatite, the caesium ore, is never placed by map generation and doesn't show on the map: you find it with survey stations, mine it at small outposts, and sort the pollucite out of the rock. A little caesium then goes a long way, into catalysts, photocathodes, scintillators, atomic clocks and atom traps.

Factorio 2.1.20 or later. Space Age and all other mods are optional.

How it plays

1. Survey. A survey station samples one chunk every 10 seconds, nearest first. When it finds a pegmatite, the patch appears, is charted and tagged, and you get a map alert and a highlighted discovery message with an ore icon, ore amount, clickable map link and notification sound. Every planet with pegmatites has a starter patch 3–6 chunks from spawn; after that, about 1 chunk in 150 holds one.
2. Mine and sort. Patches are small (30–70 tiles), scattered, and richer the further out they are. Drills feed an X-ray ore sorter at the mine: 20 ore give 1 pollucite and 16 stone. You can sort the first handful by hand.
3. Refine. Leach the pollucite in sulfuric acid to caesium alum, make caesium carbonate, and reduce it to the metal, sealed in glass ampoules because it ignites in air. About 100 ore make one caesium; one drill gives about 18 an hour.
4. Push outward. A patch lasts a few hours of steady mining, and later machines need more caesium. The magnetometer station reaches 12 chunks, seismic charges survey wherever you throw them, and a survey satellite reveals every pegmatite within 64 chunks. Richer patches wait further out, in biter country.

Every player on the same map finds the same patches: where a pegmatite is, and how big and rich it is, comes from the map seed.

Buildings

• Survey station (3×3, Geological survey, red + green in vanilla): 6-chunk range, 10 s per chunk, 250 kW. Alt-mode shows shared survey coverage in its range and its own discoveries, for example "Area surveyed 42 / 169 · Own finds: 2".
• Magnetometer station (3×3, Caesium metal): 12-chunk range, 5 s per chunk, 500 kW. It upgrades the survey station in place.
• X-ray ore sorter (3×3, Caesium processing): the mine building. Pegmatite sorting runs only here, at one sort every 2 seconds. Built with two fast inserters for material handling; hand sorting is optional.
• Well treatment station (3×3, Well treatment): brings tired oil and gas wells within 8 tiles back toward full yield with formate brine. Each treatment uses 10 brine and adds 2,000 to the most depleted well; the station pauses when every well is full. It treats infinite wells only.
• Space Age: the ioniser and ion thruster, and the orbital survey array (below).

What caesium is used for

Optional:
- Caesium catalyst: sulfuric acid with 60 acid instead of 50 from the same sulfur, at half the pollution. The catalyst is lost in 1 craft out of 50.
- Well treatment, as above.

Required in existing recipes:
- Photocathodes: 1 per laser turret and personal laser defense for their optical receivers; also night-vision equipment where its research comes after blue science.
- Scintillators: 1 per centrifuge and 2 per nuclear reactor for radiation monitoring.
- Atomic clocks: 1 per beacon as its radio frequency reference; 10 per satellite (5 with Space Exploration); 1 per space platform starter pack with Space Age.
- Atom traps (Space Age): 1 per quantum processor and 1 per 10 cryogenic science packs.

Space Age

• Pegmatites on Nauvis, Vulcanus (richer), Gleba and Fulgora (rarer); none on Aquilo.
• Ion thruster: burns caesium plasma from an ioniser (2 MW): a third of a thruster's thrust on a tenth of the fluid, with no thruster fuel or oxidizer. About 3.6 caesium an hour per thruster. Suits slow supply shuttles.
• Orbital survey array: a platform building that surveys the planet the platform is parked over, one chunk every 5 seconds.
• Aquilo takes its caesium from lithium brine: a recipe returns 90 % of the brine with some caesium carbonate, enough for cryogenic science.

Space Exploration

• Pegmatites on planets and moons, never in orbit. Core miners don't find them.
• Gamma-ray detectors take scintillator crystals, observation frames take photocathodes, SE quantum processors take atom traps, and satellites take atomic clocks.

Compatibility

Each integration turns on only when its mod is installed. Equipment with new required parts also requires the matching Caesium research, within its existing science tier; overhaul recipes are skipped if this would require later science or create a research cycle. With Manganese, Caesium processing also needs Mangalloy research (30 red science).

Modded planets with land get pegmatites too, except icy, ocean and ore-less worlds (Frozeta, Maraxsis, Apia, Panglia, Vesta, Carnova).

Getting started

1. Research Radar, Steel processing and Geological survey (red + green in vanilla; follows radar in overhauls). Build a survey station from 1 radar, 5 steel plates and 5 electronic circuits in 10 seconds and place it near your base. Its first scans find the starter patch.
2. Research Caesium processing (after sulfur processing). Mine the patch and feed the ore to an X-ray ore sorter; sort the first handful by hand if you like.
3. Leach the pollucite with sulfuric acid, make caesium carbonate, and use it for the caesium catalyst in your acid plants.
4. At blue science, Caesium metal gives the metal, photocathodes and the magnetometer station. Survey further out before the starter patch runs dry.

You can add Caesium to an existing save. Everything starts unsurveyed, and if you already researched something that now needs caesium, the Caesium research it depends on is granted.

Settings

• Pegmatite frequency and Pegmatite richness (map settings): multiply how many chunks hold a pegmatite and how rich new patches are.
• Pegmatite messages (per player): a chat line with a map link for every find.
• Unmodified recipes (startup): host recipes Caesium leaves unchanged.
• Log Caesium changes (startup).

Credits

Caesium is by fluffy_penguin, alongside Cadmium, Tellurium, Magnesium, Phosphorus, Gallium and Neodymium. Thanks to Brevven, trikop, the Planetfall/Ashier and Timeken collections, Krastorio 2 and Space Exploration, and their maintainers, for the chains this mod connects to.

Artwork is adapted from:

• Periodic Madness by MrSmoothieHuman1 (MIT): ore, mineral and part icons, the survey stations, the X-ray ore sorter, the ioniser and the orbital survey array.
• Unused Renders by Malcolm Riley (CC BY 4.0): icons.
• Sosciencity Graphics by tirisabella, Johanna Spieker and _traum (CC BY 4.0): the well treatment station.

The artwork is resized, recoloured or re-sheeted; no endorsement is implied. Some icons reference Factorio's own artwork. Code and original artwork are MIT; third-party artwork keeps its own license. Credits and licenses are included in the mod.