You are here: Home :: Area NEM :: Chemistry :: Inorganic chemistry

K.-H. Klaska, Karen Friese, G. Adiwidjaja, J. Schlüter

The crystal structure of gordaite
NaZn₄(SO₄)
(OH)₆Cl · 6 H₂O

The new mineral gordaite [14]
from the Sierra Gorda, Chile, has chemical composition
NaZn₄(SO₄)(OH)₆Cl · 6 H₂O and crystallizes trigonal with space group P-3. The lattice parameters are a =3D 8.3556( 3) Å and c =3D 13.025(1) Å. The
structure was determined using direct methods and difference Fourier maps. Structure refinement yielded a final R(F)-value of 8.19%.
The structure is characterized by brucite-like sheets of composition [Zn₆(OH)₁₂O₂]^4- which are formed by edge-shared
Zn(OH)₆ octahedra. One seventh of the octahedral sites in the sheet is vacant. Above and below these sites [Zn(OH)₃Cl]^2- tetrahedra are located sharing their basal hydroxides with six octahedra. Sulfate groups are connected to the sheets on
both sides by corner sharing. The composition for this modified layer is
[Zn^oct₆&^oct
(OH)₆Zn^tet₂(OH)₆Cl₂(SO₄)₂]^2-. To compensate for the negative charge Na⁺ ions which are octahedrally coordinated by water molecules are
incorporated between the layers. A complex hydrogen bonding system further links subsequent layers.
The structure of gordaite is closely related to that of the synthetic material Zn₄(OH)₆SO₄·
m H₂O with
m =3D 3,5 described by Bear et al. in 1986 and presumably the same material as the one investigated by MacEwan, Cruz Cumplido and Cano Ruiz (1966) who state an average chemical composition of Zn
₁₂ (OH)₁₅(SO₄)₃
Cl₃ · 
5 H₂O. A comparison to these materials as well as to Zn₅(OH)₈Cl₂ ·  H₂O described by Nowacki and Silverman in [12] is drawn.

Zeitschrift für Kristallographie, Oldenbourg Wissenschaftsverlag

Print ISSN: 0044-2968
Volume: 212, 10/1997
Pages: 704

Journal homepage (external site)

Show all available items of this journal

 

Area NEM