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Mineral · ZnS

Sphalerite

Zinc sulfide, the ore of nearly all zinc — and named for how thoroughly it deceives anyone trying to identify it.

Ore

Sphalerite is zinc sulfide and supplies almost all the world's zinc. Its old name, blende, comes from the German for deceive: it looks metallic enough to be an ore, and miners repeatedly took it for galena, but it yielded no lead and for a long time nothing else either.

It is also the quiet source of several elements that have no ores of their own. Indium, gallium and germanium substitute into the sphalerite structure in trace amounts, and are recovered from the residues of zinc refining — which is why their supply is tied to zinc demand rather than to their own.

How to identify it

Sphalerite is difficult, which is the point of its name. Colour ranges from nearly colourless through yellow and red-brown to almost black as iron replaces zinc, and the lustre shifts with it from resinous to nearly metallic.

The reliable tests are the six cleavage directions, a hardness around 3.5 to 4, and a pale streak — much paler than the mineral itself, and quite unlike galena's lead grey.

Processing

Sphalerite is separated by froth flotation, roasted to zinc oxide, and then either reduced with carbon or leached in sulfuric acid and won electrolytically. The electrolytic route dominates because it produces purer metal.

The sulfur dioxide from roasting goes to an acid plant, and the residues left after leaching are the source of the by-product metals.

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

  • Zinc — element · almost all zinc production Wikidata
  • Indium — element · a by-product of zinc refining, which is why indium supply follows zinc demand rather than its own

is an input to

  • Roasting — process · roasted to zinc oxide before reduction or electrolytic winning
  • Froth flotation — process · reactivated with copper sulfate after the lead has been floated off, which is how one ore yields two clean concentrates

is a component of

  • Skarn — rock · with galena in the distal zones, deposited furthest out where the fluid had cooled

contains

  • Sulfur — element Wikidata
  • Zinc — element Wikidata

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 Sphalerite 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

  • Sphalerite → is an ore of (almost all zinc production) → Zinc → is an input to (the addition that makes brass; it boils below copper's melting point, which is the difficulty) → Alloying and melting → produces (tin into copper — the first alloy anybody made deliberately) → Bronze → is used to make (cast in a two-piece mould with a core, which is what bronze does better than the copper it replaced) → Bronze socketed axe → is associated with → Bronze Age complete chain
  • Sphalerite → is an input to (reactivated with copper sulfate after the lead has been floated off, which is how one ore yields two clean concentrates) → Froth flotation → is used in (the process that made low-grade disseminated sulfide deposits economic, and therefore made the modern copper industry) → 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
  • Sphalerite → is an input to (roasted to zinc oxide before reduction or electrolytic winning) → Roasting → produces (as the oxide, which is then reduced — roasting is the step that makes zinc sulfide smeltable) → Zinc → is an input to (the addition that makes brass; it boils below copper's melting point, which is the difficulty) → Alloying and melting → produces (zinc dissolved into molten copper, under conditions that stop the zinc boiling off) → Brass → is used as (in air rather than seawater — brass dezincifies in chloride) → Corrosion protection
  • Sphalerite → is an ore of (a by-product of zinc refining, which is why indium supply follows zinc demand rather than its own) → Indium → is used as (as the transparent electrode in displays) → Lighting
  • Sphalerite → is a component of (with galena in the distal zones, deposited furthest out where the fluid had cooled) → Skarn
  • Sphalerite → is an ore of (almost all zinc production) → Zinc → is a source for (recovered almost entirely from zinc refining, so indium supply is set by zinc demand) → Indium → is used as (as the transparent electrode in displays) → Lighting

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