How do I identify Johannite?

Johannite can be identified by its hardness of 2 - 2.5 on the Mohs scale, Emerald-green color. Look for these key characteristics when examining specimens.

What color is Johannite?

Johannite typically appears in Emerald-green, apple-green. Color can vary depending on impurities and formation conditions.

How hard is Johannite?

Johannite has a hardness of 2 - 2.5 on the Mohs scale. This makes it a soft mineral that can be scratched easily.

Johannite

A variety of Minerals

What is Johannite?

Johannite is a rare uranium sulfate mineral. It crystallizes in the triclinic crystal system with the chemical composition Cu[UO2(OH)SO4]2·8H2O. It crystallizes in the triclinic system and develops only small prism or thin to thick tabular crystals, usually occurs as flaky or spheroidal aggregates and efflorescent coatings. Its color is emerald-green to apple-green and its streak is pale green. Johannite is a strong radioactive mineral with a calculated activity of 87,501,143 Bq/g (to the comparison: natural potassium: 31.2 Bq/g).

Etymology & Origins

Johannite was first described in 1830 by Wilhelm Karl Ritter von Haidinger. It was named for Archduke John of Austria (1782–1859), the founder of the Landesmuseum Joanneum (Styria, Austria).

Johannite Market Value Calculator

Estimate the market value of Johannite using size, quality, and finish. This preview calculator is for quick context and is not a formal appraisal.

Johannite Localities Map

See where Johannite is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.

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North ZoneCentral RidgeSouth Basin

Key Characteristics

Formation of Johannite

Johannite forms as secondary mineral by oxidation from uraninite as well as different other uranium minerals. Localities include Argentina, Czech Republic, France, Gabon, Germany, Greece, Italy, Switzerland, United Kingdom and the United States. Type locality is the “Elias Mine” in Jáchymov (Czech Republic).

Composition of Johannite

Johannite crystallizes in the triclinic crystal system in the space group P1 with the lattice parameters a = 8.92 Å, b = 9.59 Å, c = 6.84 Å; α = 110°, β = 111.98°, γ = 100.3° and one formula unit per unit cell.