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Gemstones 250x250

The Mineral jamesonite

Thick Jamesonite Crystal Needles

Jamesonite typically forms in a unique crystal habit of fine acicular crystals that appear as woven, hair-like fibers. It may also form as dense, hairy inclusions within other crystals, such as Calcite, Fluorite, and Barite. Jamesonite often forms together with the chemically similar mineral Boulangerite, and it may be very difficult to visually distinguish these two minerals. Jamesonite is named after Robert Jameson (1774-1854), a Scottish mineralogist.

Chemical Formula

Pb4FeSb6S14

Color

Lead-gray. May occasionally tarnish with an iridescent film.

Crystal System

Monoclinic

Properties

Streak
Dark gray to black
Hardness
2.5
Transparency
Opaque
Specific Gravity
5.5 - 6.0
Luster
Metallic
Cleavage
2,1
Fracture
Uneven to splintery
Tenacity
Brittle

Crystal Habits

Most often in acicular or interlocking masses of long hair-like crystals as well as thicker crystals. Also fibrous, plumose, radiating, in compact fibrous masses, reticulated, in spherical masses, in interconnected thin slender crystals, and in masses with rough crystal faces.

Additional Information

Composition
Lead antimony sulfide, often with copper and zinc
In Group
Sulfides; Sulfosalts
Striking Features
Color, crystal habits, and brittleness
Environment
Low temperature hydrothermal replacement deposits.
Rock Type
Sedimentary

Other Names

Comuccite
Feather Ore May refer to either Boulangerite or Jamesonite due to their prevalent habit forming in feathery crystal aggregates.

Uses

Jamesonite is a minor ore of lead.

Noteworthy Localities

Jamesonite is a not a common mineral. It has been found in many of the famous arsenic-rich hydrothermal replacement deposit ore localities. It was first described from Cornwall, England, where this mineral had occurred in several localities, especially St. Endellion. Fine hairy Jamesonite masses were found at Příbram, Bohemia, Czech Republic; and rounded crystal masses from the Herja Mine, Baia Mare, Maramureș Co., Romania. The Herja Mine has also produced a rare form Calcite colored dark gray from dense Jamesonite inclusions. The Yaogangxian Mine, Yizhang Co., Hunan Province, China, produces large masses of feathery Jamesonite crystals associated with Quartz.

Large crystal masses of Jamesonite of excellent quality have come from the San José Mine, Oruro Bolivia. In Mexico, fine hairy masses are known from the Noche Buena Mine, Mazapil, Zacatecas; and aggregates of unusually thick crystals have come from Concepción del Oro and Sombrerete, Zacatecas.

In the U.S., Jamesonite needles interwoven with Quartz crystals have come from the Daly-Judge Mine, Park City District, Summit Co., Utah; and parallel masses were found in the Coeur d'Alene district, Shoshone Co., Idaho.

Common Mineral Associations

Quartz, Pyrite, Chalcopyrite, Fluorite, Calcite, Stibnite

Distingushing Similar Minerals

Boulangerite - Crystal fibers are flexible.
Millerite - Color is more yellowish.
Stibnite - Crystals usually thicker.

jamesonite Photos



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