Chalcophanite

The crystal structure of the mineral chalcophanite, ZnMn307-3H20 (see Fig. II), was one of the first layer structures of manganese oxides that has been determined. 

c = 2079.4 pm). However, the general features of the crystal structure of chalcophanite are described by both symmetries, although the latter might consid- 

Similarly to Mn,Ox and related compounds, the chalcophanite structure can be interpreted as a filled Cdl2-type structure. The space in the octahedral layer is filled by an additional layer of water molecules and some foreign cations. A comparable situation is found in several hy-droxozincates, e.g., Zn5(OH)8Cl2 H20 or Zn5(OH)6(CO)3. In these compounds the layers are formed by edge-sharing zinc hydroxide octahedra, Zn(OH)6, and the space between the layers is filled with chloride and carbonate anions and some Zn2+ cations, which are located above and below vacancies in the Zn - OH layers. 

A large number of natural mineral and synthetic materials with a layered structure and strongly varying water and foreign- 

Because of the low crystallinity of J — MnOj and bimessite samples, Giovanoli et al. used high-resolution diffraction 

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Figure 8.8 Structure of chalcophanite, a Mn(IV) oxide with a layer structure, (a) Projection along the b axis showing layers of [MnOg] octahedra linked by Zn octahedra. (b) The edge-shared [MnOfi] octahedral layer viewed normal to the basal plane. The vacant octahedral sites at the origin are at the comers of a rhombus outlining the plane of Mn atoms. Note that one out of seven Mn positions is vacant, so that each Mn is...

Post, J. E. Appleman, D. E. (1988) Chalcophanite, ZnMn307.3H20 New crystal-structure determination. Amer. Mineral., 73, 1401-4. 

Chalcophanite ZnMn307 3H20 Post (1999) Rare in marine deposits. Weathering product. 

Figure 18. Principal component analysis (PCA) of EXAFS spectra, a) linear combinations of MnC03, y-MnOOH and MnS reference spectra used as unknowns. b) First four components calculated by PCA of the unknowns shown in a), c) Target transformation on y-MnOOH and chalcophanite. The reconstructed and reference spectra for y-MnOOH are identical, which indicates that this species is contained in the series of unknowns. In contrast, the two chalcophanite (ZnMn307-3H20) spectra are very different since this species is absent. 

The indicator is a minimum at C = 3, suggesting that there are three significant components. If we look at those components (Fig. 18b), we see that the first three look like EXAFS and the other five like noise. Next, we did a target transformation on each of the references from which the data were generated as well as two other Mn compounds which were not present, chalcophanite and ( ) . Figure 18c shows the results for one of the references that were used to make the data and one that was not. It is obvious which one is which. The SPOIL values bear out the conclusion reached by visual inspection, being < 1 for the three pure references,... 

Wadsley AD (1952) The structure of lithiophorite, (Al,Li)Mn02(0H)2. Acta Cryst 5 676-680 Wadsley AD (1955) The crystal structure of chalcophanite, ZnMn307.3H20. Acta Cryst 8 1165-1172 Wasserman SR, Allen PG, Shuh DK, Bucher JJ, Edelstein NM (1999) EXAFS and principal component... 

Generally, there are two major structural forms for these minerals chain or tunnel structures, and layer structures. All of these forms are comprised of MnOs octahedras. Water molecules and/or other cations (8) are ofien present at various sites in the structures. Mn oxides having a chain or tunnel structure include pyrolusite, ramsdellite, hollandite, romanechite, and todorokite. Typical structures for the chain or tunnel type Mn oxide mineral are presented in Figure 1. Lithiophorite, chalcophanite, and bimessite are examples of Mn oxide minerals havii a layer structure. Typical structural maps are shown in Figure 2. 

Figure 2. Polyhedral representations of crystal structures ofMn oxide minerals with layer structures. (A) Lithiophorite. (B) Chalcophanite. (C) Na-rich bimessite-like phase showing disordered H20/Na (light color ball) sandwiched between the Mn octahedral sheets. Adapted from (8).

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