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
General
CategorySulfate mineral
Formula
(repeating unit)
Cu[UO2(OH)SO4]2·8H2O
Strunz classification7.EB.05 (10 ed)
VI/D.21-10 (8 ed)
Dana classification31.8.2.1
Crystal systemTriclinic
Crystal classPinacoidal (1)
(same H-M symbol)
Space groupP1
Identification
ColorEmerald-green, apple-green
Crystal habitPrismatic, tabular, coatings
TwinningSimple and repeated lamellar twinning
Cleavagegood on {100}
Mohs scale hardness2 - 2.5
LusterVitreous
StreakPale green
DiaphaneityTransparent, Translucent
Specific gravity3.32, 3.27 (calc.)
Density3.32
Optical propertiesBiaxial (+/-)
Refractive indexnα = 1.572 - 1.577 ; nβ = 1.592 - 1.597 ; nγ = 1.612 - 1.616
Birefringenceδ = 0.040
Pleochroismstrong: x= colorless; y= pale yellow; z= greenish yellow or canary-yellow
2V angle90°
Other characteristics Radioactive, Bitter taste
References[1][2][3]

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 and history

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).

Occurrence

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).

Crystal structure

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.

References

Bibliography

  • Palache, P.; Berman H.; Frondel, C. (1960). "Dana's System of Mineralogy, Volume II: Halides, Nitrates, Borates, Carbonates, Sulfates, Phosphates, Arsenates, Tungstates, Molybdates, Etc. (Seventh Edition)" John Wiley and Sons, Inc., New York, pp. 606-607.
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