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).
Market Value Factors
Pricing varies for every rock and mineral, so use these universal factors to gauge Johannite before comparing listings or appraisals.
Size & Weight
Larger, intact specimens usually command higher prices.
Rarity & Demand
Scarce material or popular varieties sell at a premium.
Condition & Finish
Chips, repairs, and heavy wear lower value; clean prep helps.
Treatment & Provenance
Untreated specimens with documented locality are prized.
Johannite Localities Map
See where Johannite is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.
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.
Quick Facts
Physical Properties
- Color
- Emerald-green, apple-green
- Hardness (Mohs)
- 2 - 2.5
- Density
- 3.27 g/cm³
- Streak
- Pale green
Chemical Properties
- Chemical Formula
- Cu(UO2)2(SO4)2(OH)2 · 8H2O
- Elements
- Cu, H, O, S, U
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Johannite FAQs
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.
What is the formation of johannite 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).
What is the composition of johannite 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.
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