Acronym ...
Name hexagonal bipyramid
Vertex figure [t6], [T4]
Face vector 8, 18, 12
Confer
variations:
m m6o  
partial Stott expansions:
((oq6oo dx))&#zh  

Note that the term hexagonal dipyramid in general says nothing about the relative ratio of the edge sizes. An all-unit edged version of the hexagonal dipyramid clearly would be degenerate. This non-degenerate variant uses x-edges at the equator and h-edges for lacings. The triangles {(t,T,T)} then have vertex angles t = arccos(2/3) = 48.189685° resp. T = arccos[1/sqrt(6)] = 65.905157°.


Incidence matrix according to Dynkin symbol

((uo oq6oo))&#zh   → height = 0
                     where u = 2 (pseudo)

o. o.6o.    | 2 * |  6 0 |  6  [t6]
.o .o6.o    | * 6 |  2 2 |  4  [T4]
------------+-----+------+---
oo oo6oo&#h | 1 1 | 12 * |  2  h
.. .q ..    | 0 2 |  * 6 |  2  q
------------+-----+------+---
.. oq ..&#h | 1 2 |  2 1 | 12  {(t,T,T)}

((uo oq3oq))&#zh   → height = 0
                     where u = 2 (pseudo)

o. o.3o.    | 2 * |  6 0 0 | 3 3  [t6]
.o .o3.o    | * 6 |  2 1 1 | 2 2  [T4]
------------+-----+--------+----
oo oo3oo&#h | 1 1 | 12 * * | 1 1
.. .q ..    | 0 2 |  * 3 * | 2 0
.. .. .q    | 0 2 |  * * 3 | 0 2
------------+-----+--------+----
.. oq ..&#h | 1 2 |  2 1 0 | 6 *  {(t,T,T)}
.. .. oq&#h | 1 2 |  2 0 1 | * 6  {(t,T,T)}

oqo6ooo&#ht   → both heights = 1

o..6o..    | 1 * * | 6 0 0 | 6 0  [t6]
.o.6.o.    | * 6 * | 1 2 1 | 2 2  [T4]
..o6..o    | * * 1 | 0 0 6 | 0 6  [t6]
-----------+-------+-------+----
oo.6oo.&#h | 1 1 0 | 6 * * | 2 0
.q. ...    | 0 2 0 | * 6 * | 1 1
.oo6.oo&#h | 0 1 1 | * * 6 | 0 2
-----------+-------+-------+----
oq. ...&#h | 1 2 0 | 2 1 0 | 6 *  {(t,T,T)}
.qo ...&#h | 0 2 1 | 0 1 2 | * 6  {(t,T,T)}

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