Molybdenite
Molybdenite is a soft, metallic molybdenum sulfide and the most important ore of molybdenum. It appears as bluish lead-gray flakes, plates, and foliated masses that feel greasy and leave a mark like graphite.
Molybdenite properties at a glance
| Type | Sulfide Minerals |
|---|---|
| Chemical formula | MoS2 |
| Mohs hardness | 1.25 |
| Crystal system | hexagonal |
| Luster | metallic |
| Streak | Bluish gray |
| Cleavage | Perfect on {0001} |
| Fracture | Uneven |
| Specific gravity | 4.7 |
| Transparency | opaque |
| Common colors | Lead gray, Bluish gray |
| Rarity | uncommon |
Geology & background
Molybdenite forms in high-temperature hydrothermal environments, especially in porphyry deposits, quartz veins, pegmatites, and contact metamorphic zones around intrusive rocks.
Molybdenite was long confused with graphite and galena until eighteenth-century chemists identified the new element molybdenum within it, opening the way for modern molybdenum metallurgy.
How to identify Molybdenite
- Look for a soft, bluish lead-gray metallic mineral that feels greasy and forms flexible flakes.
- It is extremely soft, marking paper and bending into thin nonelastic plates along its perfect cleavage.
- Distinguish it from graphite by its bluish-gray streak on glazed porcelain and higher density.
Where Molybdenite is found
Molybdenite occurs in porphyry deposits, veins, and pegmatites worldwide, with notable specimen localities in the United States, Canada, China, Chile, Australia, and Norway.
How much is Molybdenite worth?
| Entry-level specimen | $8 |
|---|---|
| Typical collector specimen | $45 |
| Premium specimen | $250+ |
Value depends on crystal size, well-formed plates, matrix, locality, and aesthetic quality of the specimen.
Common uses
- Ore of molybdenum
- Solid lubricant
- Steel alloying additive
- Source of rhenium
- Collector specimens
Interesting facts
- Molybdenite is so soft it can be marked with a fingernail and feels greasy to the touch.
- It closely resembles graphite, but molybdenite leaves a bluish streak while graphite leaves a black one.
- It is the primary ore of molybdenum, a metal used to strengthen and harden steel.
- Molybdenite is sometimes a minor source of the rare element rhenium.
Care & safety
Molybdenite is very soft and easily smeared, scratched, or deformed by ordinary handling.
Avoid inhaling dust. Do not cut, grind, or polish unknown specimens without eye protection and a proper respirator.
