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Material World
Mineral · Na2B4O5(OH)4·8H2O

Borax

A hydrated sodium borate from dried desert lakes — the source of boron, and the flux that made soldering and brazing possible.

Ore

Borax crystallises where a desert lake dries out, which restricts it to a handful of places — the Tibetan plateau, the Atacama, and the Californian deserts whose twenty-mule teams hauled it out. It was a trade good moving along caravan routes long before anybody knew boron existed.

Its oldest use is as a flux. Molten borax dissolves metal oxides, so a joint painted with it is stripped clean as it heats and the solder wets bare metal rather than tarnish. Brazing and soldering are difficult without a flux and straightforward with one, and borax was the first good one.

Uses

Most borax now goes to glass. Borosilicate glass — the laboratory and cookware kind — expands so little on heating that it survives thermal shock that would crack ordinary soda-lime glass, and the boron is what does that. Glass fibre for insulation and reinforcement takes another large share.

Beyond glass it is a flux, a mild alkali in detergents, and a wood preservative and insecticide, boron being toxic to insects and fungi at concentrations people tolerate.

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

  • Boron — element · the principal source of boron compounds Wikidata

is a component of

  • Evaporite — rock · in the continental playa evaporites rather than the marine ones, where borate-rich springs fed a closed basin

is used as

  • Glass and ceramics — application · for borosilicate glass, which survives being heated and cooled quickly where soda-lime glass cracks

is a source for

  • Borosilicate glass — material · the boron source, and the ingredient the whole material is named for

contains

Sources

  • Material World
    Our own writing
  • Wikidata
    Wikimedia Foundation · Creative Commons CC0 1.0 Universal (public domain dedication)
  • Crystallography Open Database
    COD Advisory Board / Vilnius University · CC0 — contributors place data in the public domain

Questions this page answers

Where it comes from, and what it becomes

Follow Borax 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

  • Borax → is a component of (in the continental playa evaporites rather than the marine ones, where borate-rich springs fed a closed basin) → Evaporite → is a source for (mined as rock salt from bedded deposits, or dissolved in place and pumped up as brine — which is what the chemical industry wants anyway) → Salt → is an input to (the largest single use of salt, and the process the whole chlorine and caustic soda industry rests on) → Chlor-alkali electrolysis → produces (at the cathode, in fixed proportion to the chlorine whether demand agrees or not) → Sodium hydroxide → is used as (in the Bayer process and in metal cleaning before coating) → Corrosion protection
  • Borax → is a source for (the boron source, and the ingredient the whole material is named for) → Borosilicate glass → is an input to (with difficulty, which is why flat borosilicate costs several times what window glass does) → Float glass process → produces (drawn off the tin bath as a sheet flat on both surfaces) → Soda-lime glass → is used in (the envelope, which has to seal against metal without cracking as both expand) → Incandescent lamp → is used as (and almost all of the energy leaves as heat, which is inherent rather than a design failure and is why it was legislated away) → Lighting
  • Borax → is an ore of (the principal source of boron compounds) → Boron → is a component of (about one per cent, and structurally essential — the compound is Nd₂Fe₁₄B, and without the boron it does not form) → Neodymium magnet → is used as (the strongest in commercial use, and the reason a motor, a hard drive and an earbud can be small) → Permanent magnets
  • Borax → is used as (for borosilicate glass, which survives being heated and cooled quickly where soda-lime glass cracks) → Glass and ceramics
  • Borax → is an ore of (the principal source of boron compounds) → Boron → is used as (boron-10 absorbs neutrons better than almost anything, making it the standard control-rod material) → Nuclear fuel
  • Borax → is an ore of (the principal source of boron compounds) → Boron → is a component of (about one per cent, and structurally essential — the compound is Nd₂Fe₁₄B, and without the boron it does not form) → Neodymium magnet → is used in (direct-drive wind turbine generators, which is what put rare-earth supply into energy policy) → Energy generation

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