Details

Autor(en) / Beteiligte

• Števko, Martin
• Myšľan, Pavol
• Biagioni, Cristian
• Mauro, Daniela
• Mikuš, Tomáš

Titel

Ferriandrosite-(Ce), a new member of the epidote supergroup from Betliar, Slovakia

Ist Teil von

• Mineralogical magazine, 2023-12, Vol.87 (6), p.887-895

Ort / Verlag

London: Cambridge University Press

Erscheinungsjahr

2023

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Abstract A new member of the epidote supergroup, ferriandrosite-(Ce), ideally MnCeFe 3+ AlMn 2+ (Si 2 O 7 )(SiO 4 )O(OH), was found at the Július manganese ore occurrence near Betliar, Rožňava Co., Košice Region, Slovakia. It occurs as subhedral grains and polycrystalline aggregates, up to 0.3 mm in size, enclosed in pyroxmangite. Other associated minerals are spessartine, rhodochrosite, quartz, baryte and pyrosmalite-(Mn). Ferriandrosite-(Ce) is dark brown, with a light brown streak and vitreous lustre. The Mohs hardness is ~6½ to 7 and tenacity is brittle with no observable cleavage or fracture. The calculated density is 4.321 g⋅cm –3 . Ferriandrosite-(Ce) is optically biaxial (+), with weak pleochroism, high surface relief and the mean calculated refractive index is 1.832. The empirical structural formula of ferriandrosite-(Ce), based on 13 anions per formula unit, is A 1 (Mn 2+ 0.63 Ca 0.35 Ce 0.02 ) Σ1.00 A 2 (Ce 0.53 La 0.27 Nd 0.14 Pr 0.05 REE* 0.01 ) Σ1.00 M 1 (Fe 3+ 0.41 Al 0.12 V 3+ 0.01 Mg 0.40 Ti 0.05 ) Σ0.99 M 2 Al 1.00 M 3 (Mn 2+ 0.75 Fe 2+ 0.22 Mg 0.03 ) Σ1.00 T 1–3 Si 3.00 O 11 O4 (O 0.67 F 0.33 )(OH), where REE* are minor rare earth elements. Ferriandrosite-(Ce) is monoclinic, space group P 2 1 / m , a = 8.8483(4) Å, b = 5.7307(3) Å c = 10.0314(5) Å, β = 113.3659(15)°, V = 466.95(4) Å 3 and Z = 2. The crystal structure of ferriandrosite-(Ce) was refined to a final R 1 = 0.0210 for 1910 reflections with F o > 4σ( F o ) and 127 refined parameters. Structural features of ferriandrosite-(Ce) are discussed and compared with other members of the androsite-series.