Summary: Luetheite was found at a small prospect in Santa Cruz County, Arizona, as crystals in vugs in rhyolite porphyry. A few specimens were found on the dump, none seen in place. Occurs in silicified porphyry (quartzsericite-alunite) with chenevixite and hematite. Crystals indian blue inclining to greenish, H = 3, D_meas = 4·28.

Crystals monoclinic 2/m and tabular on a {100}, also a plane of distinct cleavage; other forms are {110}, {140}, {011}. Space group perhaps P2₁/m with a = 14·743Å, b = 5·093, c = 5·598, β = 101° 49′; strongest lines are 3·498Å (10), 310, 111; 7·208 (7), 200; 2·507 (5), 120, 510. Feebly pleochroic in pale blue in thin section, γ = β > α. Indices are α = 1·752, β = 1·773, γ = 1·796; 2Vγ = 88° (calc.); dispersion is moderate ν > ρ. α ∥ [010], γ: [001] 10° in obtuse β. Duplicate chemical analyses averaged CuO 28·9%, Al₂O₃ 18·4%, As₂O₅ 40·5%, H₂O 9·3% giving 2[Cu₂Al₂ (AsO₄)₂(OH)₄·H₂O].

Named for R. D. Luethe, geologist for Phelps Dodge Corporation. Chenevixite from Las Animas, Sonora, analysed to give Cu₂Fe₂(AsO₄)₂(OH)₄·H₂O. Powder data are close to luetheite, and the cell is monoclinic 2/m, probably P2₁/m, with a = 15·006A, b = 5·189, c = 5·724, β = 102°15. The measured specific gravity is 4·38, D_cale. = 4·59. Crystals tabular on a {100} with a habit very similar to luetheite. Indices are α = 1·92 , β = 1·96, γ = 2·04, 2Vγ_cale. = 75°; α ∥ [100], γ nearly ∥ [001].