MINERALS AND SYNTHETIC COMPOUNDS, AmXn, IN WHICH X ATOMS ARE
          CLOSE PACKED AND A ATOMS OCCUPY OCTAHEDRAL INTERSTICES
 
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Diaspore

                  click here to see a key to this data bar                                  

octa

50%

hcp

3-d

4 edges, 1 vertex

A- 6c, X- 3c/hcp

.

  structure

.
. .
     In the diaspore structure X anions (O and OH) are packed HCP with metal ions in .
50% of the octahedral interstices of each successive layer.  Diaspore is similar to .
rutile except that double chains of AX6 groups of atoms comprise the structure.
  .
Ex. a-AlO.OH  (aluminum oxyhydroxide, diaspore )   ( Al - A ; O , OH - X ) .
.
Crystal lattice
     The doubled rows of occupied AX6 groups in each layer are demonstrated to be
separated by doubled rows of unoccupied octahedral voids.  Like the rutile structure
these doubled rows are staggered relative to each other in each successive layer so
that they are linked by their exposed vertices.
 

diaspore.gif

 
          Figure 88  

click image

     Diaspore lattice

to enlarge

           structure
   
Polyhedral framework
.      

linking surfaces

diaspore.gif

 

Figure 89 - Diaspore

polyhedral framework

              

4 edges, 1 vertex

click image to enlarge

.      
     The doubled chains are clearly visible in the framework model as is their linkage.
The OH ions are located at the vertices of the edges linking the AX6 groups together
into the double chains.  The O atoms are located at the vertices linking the doubled
chains of each successive layer to each other. (the blue triangles are braces)
.
Cleavage

Crystal habit

     (100) - perfect, (110) - less so      tabular - parallel to (100)
   
Isostructural minerals/compounds
a-FeO.OH, a-MnO.OH, a-ScO.OH, VO.OH
.

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