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Material World
Mineral · FeAsS

Arsenopyrite

Iron arsenic sulfide — the commonest arsenic mineral, and the one that makes gold ore refractory and gold mining an arsenic problem.

Ore

Arsenopyrite is the commonest arsenic-bearing mineral and the source of most of the world's arsenic — not because anybody mines it for that, but because it comes up with the gold.

Gold frequently occurs locked inside arsenopyrite as particles too fine to liberate by crushing, which makes such ore *refractory*: cyanide cannot reach the gold. Getting it out means destroying the mineral first, by roasting or bio-oxidation, and that releases the arsenic. So arsenic production is set by gold production, and the arsenic is a waste to be managed rather than a product to be sold.

Environmental impact

Arsenopyrite weathers to release arsenic into water, and does so whether or not anybody has mined it. Where mining has crushed and exposed it, the surface area available to weathering increases by orders of magnitude, and the result is arsenic in groundwater at concentrations that are a serious public health problem in several parts of the world.

It is also a common companion of pyrite in acid mine drainage, where the acid generated by one mineral mobilises the arsenic released by the other.

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

  • Arsenic — element · the main source, though it is recovered as an unwanted by-product of gold rather than mined for itself Wikidata

is an input to

  • Roasting — process · roasted to destroy the mineral and free the gold locked inside it, which is what releases the arsenic

is commonly confused with

  • Pyrite — mineral · both brassy metallic sulfides of iron; arsenopyrite is paler and harder, and smells of garlic when struck

is a component of

  • Greisen — rock · common in the veins around a greisen, and the mineral that makes tin and tungsten concentrates awkward to smelt

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 Arsenopyrite 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

  • Arsenopyrite → is an input to (roasted to destroy the mineral and free the gold locked inside it, which is what releases the arsenic) → 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
  • Arsenopyrite → is an ore of (the main source, though it is recovered as an unwanted by-product of gold rather than mined for itself) → Arsenic → is used as (as gallium arsenide, in infrared and laser diodes) → Lighting
  • Arsenopyrite → is a component of (common in the veins around a greisen, and the mineral that makes tin and tungsten concentrates awkward to smelt) → Greisen
  • Arsenopyrite → is an input to (roasted to destroy the mineral and free the gold locked inside it, which is what releases the arsenic) → Roasting → produces (as the oxide, which is then reduced — roasting is the step that makes zinc sulfide smeltable) → 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
  • Arsenopyrite → is an input to (roasted to destroy the mineral and free the gold locked inside it, which is what releases the arsenic) → Roasting → produces (as the oxide, which is then reduced — roasting is the step that makes zinc sulfide smeltable) → Zinc → is a source for (captured from the flue dusts of zinc smelting before it disperses) → Thallium → is used as (thallium-201 as a cardiac imaging tracer) → Medical imaging
  • Arsenopyrite → is an input to (roasted to destroy the mineral and free the gold locked inside it, which is what releases the arsenic) → Roasting → produces (as the oxide, which is then reduced — roasting is the step that makes zinc sulfide smeltable) → Zinc → is a component of (typically a fifth to a third; the proportion decides whether the alloy cold-works or casts) → Brass → is used as (in air rather than seawater — brass dezincifies in chloride) → Corrosion protection

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