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The Mineral boulangerite

Boulangerite with Arsenopyrite

Boulangerite typically forms in a unique crystal habit of fine acicular crystals that appear as woven, hair-like fibers. The thin fibers, which can be very thick covering an entire specimen, or thinly spaced on a matrix, are often bent or interwoven due to their flexibility. Boulangerite also forms as dense, hairy inclusions within other crystals, especially Calcite and Quartz. Boulangerite often forms together with the chemically similar mineral Jamesonite, and may be very difficult to visually distinguish from it. Boulangerite is named after Charles Louis Boulanger (1810-1849), a French mining engineer.

Chemical Formula

Pb₅Sb₄S₁₁

Color

Lead-gray with a bluish tint. May occasionally tarnish with an iridescent film.

Crystal System

Monoclinic

Properties

Streak
Brownish gray to black

Hardness
2.5 - 3

Transparency
Opaque

Specific Gravity
6.2 - 6.3

Luster
Metallic

Cleavage
2,1

Fracture
Uneven to splintery

Tenacity
Brittle. Thin fibers flexible

Crystal Habits

Most often in acicular or interlocking masses of long hair-like crystals. Also fibrous, plumose, radiating, in compact fibrous masses, in interconnected thin slender crystals, and in massive form. An unusual habit is cylindrical rings and hollow tubes that form as a result of microscopic crystal fibers spinning naturally in a concentric pattern during formation.

Additional Information

Composition
Lead antimony sulfide

In Group
Sulfides; Sulfosalts

Striking Features
Color, crystal habits, and flexibility

Environment
Low temperature hydrothermal replacement deposits.

Rock Type
Sedimentary

Other Names

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

Varieties

Plumosite

- Feathery, plumose form of Boulangerite.

Uses

Boulangerite is a minor ore of lead.

Noteworthy Localities

One of the best localities for Boulangerite is the Noche Buena Mine, Mazapil, Zacatecas, Mexico. This locality has produced excellent examples of fibers in dense habit associated within a matrix with other ore minerals. The Yaogangxian Mine, Yizhang Co., Hunan Province, China, produces dark Boulangerite crystals of very large size, associated with Quartz, as well as included within the Quartz.

Eastern Europe has several classic localities for Boulangerite, where it occurs in the typical, hair-like habit. These include Příbram, Bohemia, Czech Republic; the Trepča complex, Kosovo; and the Herja Mine, Baia Mare, Maramureș Co., Romania (where the Boulangerite is often densely including Calcite crystals. Western European localities of note are the Ramsbeck District, North Rhine-Westphalia, Germany; La Mure, Isère, Rhône-Alpes, France; and the Bottino Mine, Stazzema, Tuscany, Italy.

Boulangerite is uncommon in the U.S. The two most important deposits are the Coeur d'Alene district, Shoshone Co., Idaho; and the Cleveland Mine, Stevens County, Washington. Canada has produced Boulangerite, especially in odd tubular form, at the Rogers Mine, Madoc, Hastings Co., Ontario.