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The Mineral pentlandite

Pentlandite, Chalcopyrite, and Pyrrhotite

Pentlandite is an important mineral due to its nickel content, but it rarely forms in interesting specimens for collectors. It usually occurs together with Pyrrhotite, and may even be intergrown together with it.

Pentlandite is both an individual mineral, and the name of a mineral group. The Pentlandite group is composed of rare sulfides that have similar chemical structures, with Pentlandite being the most prominent member of the group. Pentlandite is named in honor of Joseph Barclay Pentland (1797–1873), a natural scientist from Ireland who first identified this mineral.

Chemical Formula

(Fe,Ni)₉S₈

Color

Silvery yellow to light bronze

Crystal System

Isometric

Properties

Streak
Bronze to light brown

Hardness
3.5 - 4

Transparency
Opaque

Specific Gravity
4.6 - 5.1

Luster
Metallic

Cleavage
None. May exhibit parting in one direction.

Fracture
Conchoidal to uneven

Tenacity
Brittle

Crystal Habits

Crystals are very rare. Most often grainy, platy, and massive.

Additional Information

Composition
Iron and nickel sulfide, sometimes with some cobalt

In Group
Sulfides; Simple Sulfides

Striking Features
Color, mode of occurrence, and lack of magnetic properties.

Environment
Ultramafic nickel-rich ore deposits.

Rock Type
Igneous, Metamorphic

Uses

Pentlandite is an important ore of nickel.

Noteworthy Localities

Pentlandite is not a common mineral in collections, and few localities have produced specimens of note. The premier locality for this mineral is the Sudbury district in Ontario, Canada, especially at the Frood and Worthington Mines. Other localities include the Copper King Mine, Gold Hill, Boulder Co., Colorado; and the Bushveld Complex in Limpopo Province, South Africa. Cobalt-rich Pentlandite, known as Cobaltpentlandite, is described from the Varislahti Deposit, Karelia, Finland.