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Material World
Mineral · PbS

Galena

Lead sulfide — heavy, metallic, splitting into perfect cubes, and the ore that has supplied nearly all the world's lead since antiquity.

Ore Collectible specimen

Galena is lead sulfide, and it is unmistakable: very heavy for its size, bright metallic grey, and cleaving into cubes so cleanly that a struck specimen falls apart into smaller cubes. Those properties made it one of the first ores humans learned to smelt, because lead comes out of it at a temperature a simple hearth can reach.

Its second importance is silver. Galena commonly carries silver in solid solution, and for much of history the silver was the point and the lead was what came with it — the mines of Laurion that funded classical Athens were lead mines being worked for their silver.

How to identify it

Density and cleavage together are decisive. Galena is about seven times as dense as water, which is obvious in the hand, and its three cleavages meet at right angles so that fragments are cubes or steps of cubes.

The streak is lead grey and the lustre bright metallic on fresh surfaces, dulling to a bluish grey on exposure.

Processing

Galena is concentrated by froth flotation, then roasted to convert the sulfide to an oxide, then reduced. The sulfur dioxide from roasting is captured and made into sulfuric acid rather than released.

Silver is recovered from the lead afterwards, by a process that exploits the fact that silver prefers molten zinc to molten lead — the zinc is skimmed off carrying the silver with it.

Environmental impact

Lead is a cumulative poison with no known safe exposure, and galena mining and smelting have left contaminated ground at sites across the world. Historic smelter districts remain a soil problem long after the works have closed.

The mineral itself is stable and poorly soluble, which is why it survives in rock; the hazard arises when it is crushed, roasted or weathered into forms the body can absorb.

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

  • Lead — element · nearly all the world's lead, and historically worked as much for the silver it carries Wikidata
  • Silver — element · as a by-product, recovered from the lead after smelting

is an input to

  • Roasting — process · roasted to the oxide, the sulfur going to an acid plant rather than the air
  • Froth flotation — process · floated ahead of sphalerite, the zinc mineral being held back with a depressant and taken in a second stage

is a component of

  • Skarn — rock · the lead of the distal zones, generally alongside sphalerite rather than on its own

is commonly confused with

  • Molybdenite — mineral · both soft, heavy and metallic grey; molybdenite is named from the Greek for lead because it, graphite and galena were long taken for one substance

is an alternative to

  • Acanthite — mineral · as a source of silver, and the two are not comparable in volume. Most silver is a by-product of lead mining and comes from galena that happens to carry it; acanthite is what is mined where silver is the object rather than the bonus

contains

  • Lead — element Wikidata
  • Sulfur — 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 Galena 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

  • Galena → is an ore of (nearly all the world's lead, and historically worked as much for the silver it carries) → Lead → is a source for (most silver reaches the market as a by-product of lead mining rather than from silver mines, recovered from the refinery's residues) → Silver → is a component of (a few per cent in the lead-free alloys, which measurably raised world silver demand when the transition happened) → Solder → is used in (and the move away from tin-lead under RoHS from 2006 is the most visible material change the industry has made) → 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
  • Galena → is an ore of (as a by-product, recovered from the lead after smelting) → Silver → is a component of (a few per cent in the lead-free alloys, which measurably raised world silver demand when the transition happened) → Solder → is used in (every joint on it, and tin-silver-copper since RoHS pushed the lead out from 2006) → Printed circuit board → is used in (and it is the change that made electronics manufacturable: assembly stopped being a wiring job and became a printing one) → 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
  • Galena → is an input to (floated ahead of sphalerite, the zinc mineral being held back with a depressant and taken in a second stage) → 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
  • Galena → is an input to (roasted to the oxide, the sulfur going to an acid plant rather than the air) → 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
  • Galena → is a component of (the lead of the distal zones, generally alongside sphalerite rather than on its own) → Skarn
  • Galena → is an ore of (nearly all the world's lead, and historically worked as much for the silver it carries) → Lead → is associated with (lead was smelted alongside copper from the earliest metallurgy) → Bronze Age complete chain

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