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The Mineral natrojarosite

Massive Natrojarosite

Chemical Formula

NaFe³⁺₃(SO₄)₂(OH)₆

Color

Yellow-brown to brown

Crystal System

Hexagonal

Properties

Streak
Light yellow

Hardness
3 - 3.5

Transparency
Translucent

Specific Gravity
3.1 - 3.3

Luster
Resinous to adamantine

Cleavage
2,1 - basal (usually cannot be determined)

Fracture
Conchoidal, uneven

Tenacity
Brittle

Crystal Habits

Only in very small crystals, which are hexagonal or triangular shaped, and may also be tabular or pseudocubic. Also grainy, as fibrous crusts, in nodules, and in thin, hexagonal scales.

Additional Information

Composition
Basic hydrous sodium iron sulfate

In Group
Sulfates; Hydrous Sulfates

Striking Features
Crystal habits and color

Environment
As a secondary mineral that forms through weathering in arid regions.

Rock Type
Sedimentary, Metamorphic

Noteworthy Localities

Natrojarosite has been found in Lavrion, Greece; the Francon Quarry, Montreal, Quebec, Canada; Rapid Creek area, Yukon Territory, Canada; and Palos Verdes Hills, Los Angeles Co., California.

Common Mineral Associations

Goethite, Pyrite, Galena, Barite

Distingushing Similar Minerals

Natrojarosite's crystal forms combined with its color easily identify it. However, poorly crystallized examples and massive forms of Natrojarosite may be difficult to distinguish from other minerals, such as Limonite. Natrojarosite is also indistinguishable from its isomorphous mineral Jarosite by ordinary methods.