Mineral · (Ce,La,Nd,Th)PO4

Monazite

A rare earth phosphate that carries thorium with it — the other major rare earth ore, and the reason their processing leaves radioactive residues.

Ore

Monazite is a phosphate of the light rare earths, written with cerium, lanthanum and neodymium bracketed together because the mineral takes whichever is available. Alongside bastnäsite it is one of the two ores the world's rare earths come from.

What distinguishes it is thorium. The thorium ion is close enough in size and charge to the rare earths to substitute into the same site, so monazite is radioactive — mildly, but enough that its residues are regulated as radioactive waste. That is not a detail. It is a large part of why rare earth separation is concentrated in so few countries, and why reopening capacity elsewhere has proved slower than opening mines.

Extraction

Monazite is chemically tough and physically dense, so it survives weathering and transport and accumulates in heavy mineral sands with zircon, rutile and ilmenite. Much of it is recovered as a by-product of mining those sands for titanium.

That co-occurrence means monazite is often produced whether or not anybody wants it, and stockpiles accumulate where the thorium makes disposal awkward and processing unattractive.

Medium confidence Weak evidence

How we know: checked recently · only one source, so there is nothing to cross-check it against · stated directly by the source.

How this connects

Where a connection has been confirmed by an outside reference, that reference is named beside it.

is an ore of

Neodymium — element · one of the two major rare earth ores, alongside bastnäsite
Thorium — element · historically the principal source of thorium, which substitutes into the rare earth site

is an input to

Rare earth separation — process · the other feed alongside bastnäsite, bringing thorium into the residues with it

is a component of

Pegmatite — rock · an accessory of rare-element pegmatites rather than a defining constituent — carrying the light rare earths and the thorium with them
Carbonatite — rock · the rare earth phosphate, carrying thorium with it — which is the difficulty rather than the resource
Granite — rock · in the more evolved granites, carrying the light rare earths and the thorium that goes with them

is a source for

Mischmetal — alloy · reduced from the mixed light rare earths that monazite and bastnäsite deliver, in the proportions the ore happened to contain

is an alternative to

Bastnäsite — mineral · as light rare earth ore, and the deciding factor is thorium: monazite carries enough to make the residue a radioactive waste problem and bastnäsite carries far less, which is why the large operations are bastnäsite and monazite is mostly a by-product

contains

Cerium — element · substitutes within a solid solution — an individual specimen may hold little of it
Lanthanum — element · substitutes within a solid solution — an individual specimen may hold little of it
Neodymium — element · substitutes within a solid solution — an individual specimen may hold little of it
Oxygen — element
Phosphorus — element
Thorium — element · substitutes within a solid solution — an individual specimen may hold little of it

Sources

Material World
Our own writing
Wikidata
Wikimedia Foundation · Creative Commons CC0 1.0 Universal (public domain dedication)

Where it comes from, and what it becomes

Follow Monazite back to what it starts as, and forward into what it becomes. Each step is a documented one — a real route material takes, not a chain of inference.

Downstream — what it becomes

Monazite → is an ore of (one of the two major rare earth ores, alongside bastnäsite) → Neodymium → is used in (in the speaker, the microphone and the vibration motor, as the magnet alloy) → Smartphone → is used in (and it is where four separate raw-material arguments meet — the 3TG conflict minerals, cobalt, the rare earths, and everything too dispersed to recover) → Electronics manufacture → is associated with (and the supply chain it produced is the deepest and most concentrated in the world economy) → The semiconductor era complete chain
Monazite → is a component of (in the more evolved granites, carrying the light rare earths and the thorium that goes with them) → Granite → is a source for (quarried in blocks for cladding, kerbs and monuments) → Dimension stone → is used in (quarried rather than mined, and the distinction is legal and technical rather than merely a word) → Mining and quarrying → is associated with (steam pumping allowed mines below the water table, which is what made deep coal possible) → Industrial Revolution complete chain
Monazite → is an input to (the other feed alongside bastnäsite, bringing thorium into the residues with it) → Rare earth separation → produces (a light rare earth, separated from its neighbours by countercurrent solvent extraction) → Lanthanum → is a component of (roughly a quarter, again as the ore gave it) → Mischmetal → is used as (added to molten steel to scavenge sulfur and oxygen and reshape the inclusions that remain, which improves toughness — an unglamorous use that consumes a great deal of it) → Alloying
Monazite → is an ore of (historically the principal source of thorium, which substitutes into the rare earth site) → Thorium → is used as (not itself fissile — it breeds uranium-233) → Nuclear fuel
Monazite → is a source for (reduced from the mixed light rare earths that monazite and bastnäsite deliver, in the proportions the ore happened to contain) → Mischmetal → is used as (added to molten steel to scavenge sulfur and oxygen and reshape the inclusions that remain, which improves toughness — an unglamorous use that consumes a great deal of it) → Alloying
Monazite → is a component of (an accessory of rare-element pegmatites rather than a defining constituent — carrying the light rare earths and the thorium with them) → Pegmatite

These are the most distinct paths onward. Monazite ends up in others besides.