Katsarosite Zn(C2O4)·2H2O, a new humboldtine-group mineral from the Lavrion Mining District, Greece

• Published in: Mineralogy and petrology Vol. 117; no. 2; pp. 259 - 267
• Main Authors: Giester, Gerald, Rieck, Branko, Lengauer, Christian L., Kolitsch, Uwe, Nasdala, Lutz
• Format: Journal Article
• Language: English
• Published: Vienna Springer Vienna 01-06-2023; Springer Nature B.V
• Subjects: Anions; Chemical analysis; Colour; Crystal structure; Crystals; Diameters; Earth and Environmental Science; Earth Sciences; Geochemistry; Gypsum; Hydrogen bonding; Hydrogen bonds; Hydrozincite; Inorganic Chemistry; Iron; Jarosite; Long wave radiation; Mineralogy; Minerals; Mining; Morphology; Refractivity; Resins; Scratch hardness; Single crystals; Sphalerite; Ultraviolet radiation; Unit cell; Water hardness; Wavelength; X rays; X-ray diffraction; Zinc; Zinc oxide; Zincblende; Greece; Lavrion Mining District; Zinc oxalate dihydrate; Katsarosite; Zn(C; New mineral; 2H; Humboldtine group; O; Esperanza Mine; Crystal structure
• ISSN: 0930-0708; 1438-1168
• DOI: 10.1007/s00710-023-00810-9

Katsarosite, ideally Zn(C
2
O
4
)·2H
2
O, named for Īraklīs Katsaros, is a new mineral found at the Esperanza Mine in the Kaminiza area of the Lavrion Mining District, Greece. Katsarosite usually occurs directly on sphalerite or embedded in jarosite and/or hydrozincite, often intimately intergrown with gypsum and overgrown by goslarite and/or epsomite. Crystal aggregates are mostly fine granular to earthy, with individual crystals being usually rounded with an average diameter of 30 µm, sometimes prismatic along [001] or platy, exhibiting the indistinct forms {100}, {001}, {110}, and {101}. Katsarosite is malleable with a Mohs hardness of 1½ – 2 and exhibits a perfect cleavage on {110}; the fracture is uneven in all other directions. The colour depends on the iron (Fe
2+
) content, ranging from pure white in almost Fe-free samples to yellow in Fe-rich specimens. It has a resinous luster and a white streak; no luminescence has been observed under either short- or long-wave ultraviolet radiation. Katsarosite is optically biaxial (+). Refractive indices measured at a wavelength of 589 nm are
n
α
 = 1.488(2),
n
β
 = 1.550(2),
n
γ
 = 1.684(2), with 2
V
obs
 = 71(3)°. Chemical analysis gave on average C
2
O
3
38.32 wt%, ZnO 38.99 wt%, FeO 1.92 wt%, and H
2
O 19.04 wt% (the latter was deduced based on the crystal-structure refinement), with traces of MgO and MnO. The new mineral is readily soluble in dilute acids. Katsarosite is monoclinic, space group
C
2/
c
, with unit-cell parameters
a
 = 11.768(3),
b
 = 5.3882(12),
c
 = 9.804(2) Å,
β
 = 127.045(8)°,
V
 = 496.2(2) Å
3
(
Z
 = 4). The strongest lines in the Gandolfi X-ray powder pattern [
d
obs
in Å,
I
obs
/
I
100
, (
hkl
)] are: 4.6745, 100, (200); 4.7678, 94, (20
2
¯
); 2.9533, 51, (40
2
¯
); 4.7030, 37, (1
1
¯
1
¯
); 3.9266, 33, (002); 3.5686, 27, (111); 2.6574, 22, (1
1
¯
3
¯
); 3.5992, 8, (1
1
¯
2
¯
); 2.7032, 4, (020). The crystal structure was refined based on single-crystal X-ray diffraction data to
R
(
F
) = 0.08. The observed mass density of 2.50(2) g cm
−3
compares well with the calculated value (2.508 g cm
−3
). Katsarosite belongs to the humboldtine group, whose crystal-structure type is well described for both isotypic minerals and synthetic compounds in the literature. The atomic arrangement in Zn(C
2
O
4
)·2H
2
O is characterized by chains consisting of isolated ZnO
6
octahedra which are alternately linked along [010] via oxalate anions. These chains are interconnected through hydrogen bonds only, with Ow···O (with Ow denoting the O atom of the H
2
O molecule) donor–acceptor distances of ~ 2.8 Å.