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MINERALS AND SYNTHETIC COMPOUNDS, AmXn, IN WHICH X
ATOMS ARE |
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CLOSE PACKED AND A ATOMS OCCUPY OCTAHEDRAL INTERSTICES |
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Gibbsite |
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click here to see a key to this data bar
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octa |
1/3 |
ABBAA |
layer |
3
edges |
A-
6c, X- 2c/ABBAA |
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structure |
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Gibbsite is a naturally
occurring polymorph of bayerite which is identical in |
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structure except that the alternating occupied
close packed layers stack together in |
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the HP (simple hexagon) sequence.
Therefore the sequencing is ABBAABB... |
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Ex. Al(OH)3 ( aluminum
hydroxide, gibbsite ) ( Al - A , OH - X ) |
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Crystal lattice |
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The HP layering
sequence of the hexagonal nets of AX6 coordination groups of |
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atoms is clearly demonstrated by the lattice
model. The 2/3 occupancy rate of the |
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octahedral voids of these occupied layers can
also be extracted from the model. |
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Figure 94 - Gibbsite lattice structure |
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click image to enlarge |
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Polyhedral framework |
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linking surfaces |
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Figure 95 -
Gibbsite polyhedral |
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framework model |
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( 72 T, 3 S, 132 pinges ) |
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3
edges |
click image to enlarge |
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The polyhedral
framework model demonstrates the HP sequence of the hexagonal |
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rings of the occupied layers ( black squares are
braces to separate and properly orient |
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the layers). |
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Cleavage |
Crystal habit |
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(100) - perfect |
hexagonal tabular |
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Page
61 - Structure matters - Gibbsite |
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