The crystal structure of kraisslite, ^[4]Zn₃(Mn, Mg)₂₅(Fe³⁺,Al)(As³⁺O₃)₂[(Si,As⁵⁺)O₄]₁₀(OH)₁₆, from the Sterling Hill mine, Ogdensburg, Sussex County, New Jersey, USA

Abstract The crystal structure of kraisslite, orthorhombic (pseudo-hexagonal), a = 8.1821(1), b = 14.1946(3), c = 43.9103(8) Å, V = 5099.8(2) Å 3 , Z = 4 and d calc = 4.083 g cm –3 , has been solved by direct methods and refined in the space group C 222 1 to an R 1 index of 1.68% for 7432 observed (| F o | > 4σ| F |) reflections. Electron-microprobe analysis gave the following chemical composition: As 2 O 5 10.86, As 2 O 3 6.18, SiO 2 13.39, Al 2 O 3 0.25, Fe 2 O 3 2.06, MnO 51.14, ZnO 7.39, MgO 2.13, CaO 0.05, H 2 O calc = 4.50, sum 97.95 wt.%; and empirical formula: Zn 2.91 (Mn 23.07 Mg 1.69 Ca 0.03 ) Σ=24.79 (Fe 0.83 3+ Al 0.16 ) Σ=0.99 (As 3+ O 3 ) 2 [(Si 0.71 As 0.30 5+ )O 4 ] 10 (OH) 16 calculated on the basis of 62 anions with (OH) = 16 and As 3+ /(As 3+ + As 5+ ) taken from the refined crystal structure. The general formula, [4]Zn3(Mn,Mg)25(Fe 3+ ,Al)(As 3+ O 3 ) 2 [(Si,As 5+ )O 4 ] 10 (OH) 16 , differs from those given previously. There is one As 3+ site with a <As–O> distance of 1.780 Å and a stereochemistry typical of a stereoactive lone-pair of electrons. There are five tetrahedrally coordinated T sites with <T–O> distances from 1.635 to 1.692 Å; the T(1) site is fully occupied by As 5+ , and the T(2)–T(5) sites are occupied by both Si and As 5+ . There are two tetrahedrally coordinated Zn sites with <T–O> distances of ∼1.996 Å, both of which are occupied by dominant Zn and minor Mn 2+ . There are thirteen octahedrally coordinated M sites, twelve of which are occupied by dominant Mn 2+ with lesser Mg and minor Zn; <M–O> distances are in the range 2.197–2.284 Å. The <M(13)–O> distance is 2.083 Å and its lower site scattering indicates occupancy by Fe 3+ , Mn 2+ , Mg and Al. The structure consists of five crystallographically distinct layers of polyhedra, labelled m = 0 – 4. Layer m = 0 consists of corner-sharing Zn and (Si, As 5+ ) tetrahedra, and layers m = 1–4 each consist of trimers of Mn 2+ octahedra linked by (Si, As5+) tetrahedra and intrasheet hydrogen bonds (m = 1, 3) or (Si, As 5+ ) tetrahedra and (Fe 3+ ,Al) octahedra (m = 2) or (As 5+ ) tetrahedra and (As 3+ O3) triangular pyramids and intrasheet hydrogen bonds (m = 4). The layers stack along [001] with reversals of the sequence m = 1, 2, 3, 4 at z = 0, ¼, ½ and ¾. Kraisslite is a member of the mcgovernite family.

Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.