Element · Rb

Rubidium

A soft metal that ignites in air and keeps time well enough to steer satellites.

Rubidium is an alkali metal, soft enough to cut and reactive enough to catch fire in air, which rules out almost every structural use. What it is good for is a transition between two energy levels in its atoms that occurs at a very precise and reproducible frequency.

A rubidium standard is not the most accurate clock available, but it is small, cheap and robust — and those three properties are what put atomic timekeeping into telecommunications networks and satellites rather than leaving it in national laboratories.

Uses

Rubidium frequency standards are the main use: compact atomic clocks for network synchronisation, navigation satellites and test equipment, where caesium's greater accuracy is not worth its cost or size.

Rubidium is also used in photocells and in specialist glasses, and a rubidium isotope serves as a tracer in cardiac imaging because the body handles it much as it handles potassium.

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 used as

Timekeeping — application · less accurate than caesium and small enough to fly, which is what put atomic clocks into satellites and networks

is extracted from

Lepidolite — mineral · the main mineral source of rubidium, which substitutes for potassium in the mica

is produced by

Metallothermic reduction — process · reduced from its chloride the same way, and usually as a by-product of the caesium it accompanies in pollucite

Sources

Material World
Our own writing
Wikidata
Wikimedia Foundation · Creative Commons CC0 1.0 Universal (public domain dedication)
PubChem
US National Library of Medicine · Mixed — aggregated third-party content, rights retained by depositors

Questions this page answers

Where it comes from, and what it becomes

Follow Rubidium 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.

Upstream — what it comes from

Rubidium → is produced by (reduced from its chloride the same way, and usually as a by-product of the caesium it accompanies in pollucite) → Metallothermic reduction → takes as input (the cheapest reducing metal and the commonest, and the aluminium in thermite) → Aluminium → is extracted from (via alumina — bauxite is refined by the Bayer process before smelting) → Bauxite → is sourced from (the residue of prolonged tropical weathering, which strips the silica and alkalis out of an aluminosilicate rock and leaves the aluminium behind — basalt is one common parent among several) → Basalt → is composed of (an early-crystallising constituent of basaltic magma) → Olivine
Rubidium → is extracted from (the main mineral source of rubidium, which substitutes for potassium in the mica) → Lepidolite
Rubidium → is produced by (reduced from its chloride the same way, and usually as a by-product of the caesium it accompanies in pollucite) → Metallothermic reduction → takes as input (reserved for halides and the most stubborn oxides, where the cheaper metals will not do the job) → Calcium → is produced by (from molten calcium chloride; there is no smelting route) → Molten salt electrolysis → takes as input (after concentration, as one of the two routes to lithium chloride) → Lepidolite
Rubidium → is produced by (reduced from its chloride the same way, and usually as a by-product of the caesium it accompanies in pollucite) → Metallothermic reduction → takes as input (the cheapest reducing metal and the commonest, and the aluminium in thermite) → Aluminium → is produced by (collects at the cathode while the carbon anodes are consumed) → Hall–Héroult process → takes as input (dissolved in molten cryolite and electrolysed) → Aluminium oxide → is sourced from (dissolved out with hot caustic soda in the Bayer process) → Bauxite
Rubidium → is produced by (reduced from its chloride the same way, and usually as a by-product of the caesium it accompanies in pollucite) → Metallothermic reduction → takes as input (the cheapest reducing metal and the commonest, and the aluminium in thermite) → Aluminium → is extracted from (via alumina — bauxite is refined by the Bayer process before smelting) → Bauxite → is sourced from (the residue of prolonged tropical weathering, which strips the silica and alkalis out of an aluminosilicate rock and leaves the aluminium behind — basalt is one common parent among several) → Basalt → is composed of (calcium-rich plagioclase is a defining constituent of basalt) → Plagioclase
Rubidium → is produced by (reduced from its chloride the same way, and usually as a by-product of the caesium it accompanies in pollucite) → Metallothermic reduction → takes as input (the cheapest reducing metal and the commonest, and the aluminium in thermite) → Aluminium → is extracted from (via alumina — bauxite is refined by the Bayer process before smelting) → Bauxite → is sourced from (the residue of prolonged tropical weathering, which strips the silica and alkalis out of an aluminosilicate rock and leaves the aluminium behind — basalt is one common parent among several) → Basalt → is sourced from (partial melting of mantle peridotite is what basalt magma is — the residue left behind stays peridotite, depleted of what went into the melt) → Peridotite

These are the most distinct paths back. Rubidium can be traced through others besides.

Downstream — what it becomes

Rubidium → is used as (less accurate than caesium and small enough to fly, which is what put atomic clocks into satellites and networks) → Timekeeping