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Mineral · MoS2

Molybdenite

Molybdenum disulfide — the ore of molybdenum, a dry lubricant that works where oil burns, and so soft it marks paper like graphite.

Ore

Molybdenite is built in sheets held together by weak forces, exactly like graphite, and it behaves the same way: soft enough to mark paper, greasy to the touch, and an excellent dry lubricant because the sheets shear over one another under load.

That similarity fooled people for a long time. The name comes from the Greek for lead, because molybdenite, graphite and galena were all taken for the same substance, and the mineral was not distinguished from graphite until the eighteenth century.

Uses

Most molybdenite is roasted to the oxide and used to make ferromolybdenum for steel, where under a percent of molybdenum improves strength at high temperature and resistance to pitting corrosion. That is what puts it in pipeline steel, pressure vessels and the better grades of stainless.

A smaller share is used as the mineral itself: molybdenum disulfide is the dry lubricant of choice where oil would burn off, freeze or attract dust — in vacuum, in space and in high-temperature bearings.

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

  • Molybdenum — element · the principal ore, and the flue dusts of roasting it are where rhenium comes from Wikidata

is an input to

  • Roasting — process · roasted to the oxide; the flue dust carries the rhenium
  • Froth flotation — process · naturally water-repellent, so it floats almost without a collector — and is separated from copper concentrate rather than from the ore

is commonly confused with

  • Graphite — mineral · the reason molybdenite is named after lead: it, graphite and galena were long taken for one substance
  • Galena — 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 a component of

  • Greisen — rock · with the tin and tungsten, from the same vapour and often at a slightly different level
  • Porphyry copper deposit — deposit type · the reason most molybdenum is a copper by-product — and, through the rhenium it carries, the reason rhenium has a supply

is an alternative to

  • Graphite — mineral · as a dry lubricant. Both are layered structures that shear easily, and molybdenite keeps working in vacuum where graphite fails — graphite needs adsorbed water to be slippery at all, which is why it stopped working on spacecraft

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 Molybdenite 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

  • Molybdenite → is an ore of (the principal ore, and the flue dusts of roasting it are where rhenium comes from) → Molybdenum → is a source for (recovered from the flue dusts of molybdenum roasting; rhenium forms no ore of its own) → Rhenium → is a component of (two or three per cent, and essentially the only use rhenium has — most of world consumption goes into turbine blades) → Nickel superalloy → is used in (cast as a single crystal, because at temperature and sustained load the failure mode is creep along grain boundaries — so the boundaries are removed entirely) → Turbine blade → is associated with (the jet engine created the superalloy industry, because no existing material survived the turbine inlet — and turbine temperature has risen about 500 °C since, almost entirely on the blade) → The wartime materials programmes complete chain
  • Molybdenite → is an input to (naturally water-repellent, so it floats almost without a collector — and is separated from copper concentrate rather than from the ore) → 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
  • Molybdenite → is an input to (roasted to the oxide; the flue dust carries the rhenium) → 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
  • Molybdenite → is a component of (the reason most molybdenum is a copper by-product — and, through the rhenium it carries, the reason rhenium has a supply) → Porphyry copper deposit → is a source for (the weathered cap of a sulfide body rather than a deposit in its own right: the same metal, rebuilt in place by air and water) → Oxidised zone
  • Molybdenite → is a component of (with the tin and tungsten, from the same vapour and often at a slightly different level) → Greisen
  • Molybdenite → is an ore of (the principal ore, and the flue dusts of roasting it are where rhenium comes from) → Molybdenum → is used as (raises the temperature at which steel loses strength) → Alloying

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