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Six Sided Cumengite Star Habit
HALIDES · TETRAGONAL

Cumengeite

Pb21Cu20Cl42(OH)40· 6H2O

Hardness
2.5
Streak
Blue
Spec. Gravity
4.5–5
System
Tetragonal

About

Cumengeite is an uncommon mineral that forms some of the most interesting crystal shapes of all minerals. Its most famous habit is as epitaxial overgrowths over Boleite, where a single specimen has an inner cubic core of Boleite, and outer protruding crystal faces of Cumengeite in triangular habit, forming a star-like formation.
Cumengeite has been found in several localities worldwide, however, its only significant source was the the Amelia Mine in Baja California, Mexico. To date, this is the only only locality that had produced this mineral in well-formed crystals of any significance.
Cumengeite is named for Edouard Cumenge (1828-1902), a French mining engineer who was among the first to collect this mineral at its type locality of Boleo, Mexico.

Crystal Forms & Aggregates

In single crystals indipyramidal habit, resembling an elongated octahedron with central cubic faces. Also in epitaxial overgrowths of pyramidal crystals on Boleite crystal faces, forming six-sided star-shaped crystal formations which may resemble a Star of David.

Striking Features

Color, crystal habits, and localities

Environment

In the oxidation zone deposits of copper and lead.

Uses

A rare collectors mineral, with good epitaxial crystals being highly valuable.

Noteworthy Localities

The premier locality for Cumengeite, which is also the type locality, is the Amelia mine, Santa Rosalia (Boleo), Baja California Sur, Mexico. This is the only area where Cumengeite occurs as relatively large crystals.

Common Mineral Associations

Distinguishing Similar Minerals

The unique crystal formations and locality can distinguish this mineral from all other minerals.

Photos