The compound described by Ca8MgAl6Si5O28 crystallizes in the triclinic P1 space group. There are eight inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 6-coordinate geometry to one O(11), one O(15), one O(17), one O(24), one O(28), and one O(8) atom. In the second Ca site, Ca(2) is bonded in a 7-coordinate geometry to one O(12), one O(16), one O(25), one O(4), one O(5), one O(6), and one O(7) atom. In the third Ca site, Ca(3) is bonded in a 5-coordinate geometry to one O(12), one O(28), one O(6), one O(8), and one O(9) atom. In the fourth Ca site, Ca(4) is bonded in a 8-coordinate geometry to one O(10), one O(13), one O(15), one O(19), one O(24), one O(4), one O(7), and one O(9) atom. In the fifth Ca site, Ca(5) is bonded to one O(12), one O(13), one O(14), one O(23), one O(3), one O(7), and one O(8) atom to form distorted CaO7 pentagonal bipyramids that share  a cornercorner with one Al(4)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra,  a cornercorner with one Si(5)O4 tetrahedra,  a cornercorner with one Ca(7)O5 trigonal bipyramid,  a cornercorner with one Mg(1)O5 trigonal bipyramid, and  an edgeedge with one Al(3)O5 trigonal bipyramid. In the sixth Ca site, Ca(6) is bonded in a 7-coordinate geometry to one O(13), one O(14), one O(16), one O(17), one O(18), one O(22), and one O(25) atom. In the seventh Ca site, Ca(7) is bonded to one O(10), one O(20), one O(22), one O(27), and one O(7) atom to form distorted CaO5 trigonal bipyramids that share  a cornercorner with one Ca(5)O7 pentagonal bipyramid,  a cornercorner with one Al(5)O4 tetrahedra,  a cornercorner with one Al(6)O4 tetrahedra,  a cornercorner with one Si(5)O4 tetrahedra,  a cornercorner with one Al(2)O5 trigonal bipyramid,  an edgeedge with one Si(2)O4 tetrahedra, and  an edgeedge with one Al(3)O5 trigonal bipyramid. In the eighth Ca site, Ca(8) is bonded in a distorted pentagonal planar geometry to one O(2), one O(20), one O(26), one O(3), and one O(5) atom. Mg(1) is bonded to one O(11), one O(18), one O(19), one O(3), and one O(9) atom to form distorted MgO5 trigonal bipyramids that share  a cornercorner with one Ca(5)O7 pentagonal bipyramid,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra,  a cornercorner with one Si(5)O4 tetrahedra, and  an edgeedge with one Al(4)O4 tetrahedra. There are six inequivalent Al sites. In the first Al site, Al(1) is bonded in a distorted rectangular see-saw-like geometry to one O(14), one O(23), one O(25), and one O(5) atom. In the second Al site, Al(2) is bonded to one O(16), one O(24), one O(27), one O(28), and one O(6) atom to form AlO5 trigonal bipyramids that share  a cornercorner with one Al(4)O4 tetrahedra,  a cornercorner with one Al(6)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Ca(7)O5 trigonal bipyramid, and  an edgeedge with one Si(5)O4 tetrahedra. In the third Al site, Al(3) is bonded to one O(13), one O(20), one O(22), one O(5), and one O(8) atom to form AlO5 trigonal bipyramids that share  a cornercorner with one Al(5)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra,  an edgeedge with one Ca(5)O7 pentagonal bipyramid, and  an edgeedge with one Ca(7)O5 trigonal bipyramid. In the fourth Al site, Al(4) is bonded to one O(26), one O(3), one O(6), and one O(9) atom to form AlO4 tetrahedra that share  a cornercorner with one Ca(5)O7 pentagonal bipyramid,  a cornercorner with one Al(2)O5 trigonal bipyramid, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. In the fifth Al site, Al(5) is bonded to one O(1), one O(15), one O(21), and one O(22) atom to form AlO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra,  a cornercorner with one Ca(7)O5 trigonal bipyramid, and  a cornercorner with one Al(3)O5 trigonal bipyramid. In the sixth Al site, Al(6) is bonded to one O(10), one O(2), one O(24), and one O(4) atom to form AlO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra,  a cornercorner with one Ca(7)O5 trigonal bipyramid, and  a cornercorner with one Al(2)O5 trigonal bipyramid. There are five inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(18), one O(2), one O(21), and one O(23) atom to form SiO4 tetrahedra that share  a cornercorner with one Ca(5)O7 pentagonal bipyramid,  a cornercorner with one Al(5)O4 tetrahedra,  a cornercorner with one Al(6)O4 tetrahedra, and  a cornercorner with one Mg(1)O5 trigonal bipyramid. In the second Si site, Si(2) is bonded to one O(17), one O(20), one O(25), and one O(27) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(2)O5 trigonal bipyramid,  a cornercorner with one Al(3)O5 trigonal bipyramid, and  an edgeedge with one Ca(7)O5 trigonal bipyramid. In the third Si site, Si(3) is bonded in a distorted trigonal non-coplanar geometry to one O(1), one O(10), and one O(26) atom. In the fourth Si site, Si(4) is bonded to one O(11), one O(12), one O(15), and one O(4) atom to form SiO4 tetrahedra that share  a cornercorner with one Ca(5)O7 pentagonal bipyramid,  a cornercorner with one Al(5)O4 tetrahedra,  a cornercorner with one Al(6)O4 tetrahedra, and  a cornercorner with one Mg(1)O5 trigonal bipyramid. In the fifth Si site, Si(5) is bonded to one O(16), one O(19), one O(28), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Ca(5)O7 pentagonal bipyramid,  a cornercorner with one Ca(7)O5 trigonal bipyramid,  a cornercorner with one Mg(1)O5 trigonal bipyramid, and  an edgeedge with one Al(2)O5 trigonal bipyramid. There are twenty-eight inequivalent O sites. In the first O site, O(1) is bonded in a water-like geometry to one Al(5) and one Si(3) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Ca(8), one Al(6), and one Si(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ca(5), one Ca(8), one Mg(1), and one Al(4) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Ca(2), one Ca(4), one Al(6), and one Si(4) atom. In the fifth O site, O(5) is bonded in a distorted see-saw-like geometry to one Ca(2), one Ca(8), one Al(1), and one Al(3) atom. In the sixth O site, O(6) is bonded to one Ca(2), one Ca(3), one Al(2), and one Al(4) atom to form distorted OCa2Al2 trigonal pyramids that share  a cornercorner with one O(25)Ca2AlSi trigonal pyramid,  an edgeedge with one O(16)Ca2AlSi trigonal pyramid, and  an edgeedge with one O(12)Ca3Si trigonal pyramid. In the seventh O site, O(7) is bonded in a 5-coordinate geometry to one Ca(2), one Ca(4), one Ca(5), one Ca(7), and one Si(5) atom. In the eighth O site, O(8) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(3), one Ca(5), and one Al(3) atom. In the ninth O site, O(9) is bonded in a distorted rectangular see-saw-like geometry to one Ca(3), one Ca(4), one Mg(1), and one Al(4) atom. In the tenth O site, O(10) is bonded in a distorted rectangular see-saw-like geometry to one Ca(4), one Ca(7), one Al(6), and one Si(3) atom. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to one Ca(1), one Mg(1), and one Si(4) atom. In the twelfth O site, O(12) is bonded to one Ca(2), one Ca(3), one Ca(5), and one Si(4) atom to form distorted OCa3Si trigonal pyramids that share  a cornercorner with one O(15)Ca2AlSi trigonal pyramid,  a cornercorner with one O(16)Ca2AlSi trigonal pyramid,  a cornercorner with one O(25)Ca2AlSi trigonal pyramid, and  an edgeedge with one O(6)Ca2Al2 trigonal pyramid. In the thirteenth O site, O(13) is bonded in a 5-coordinate geometry to one Ca(4), one Ca(5), one Ca(6), one Al(3), and one O(14) atom. In the fourteenth O site, O(14) is bonded in a 4-coordinate geometry to one Ca(5), one Ca(6), one Al(1), and one O(13) atom. In the fifteenth O site, O(15) is bonded to one Ca(1), one Ca(4), one Al(5), and one Si(4) atom to form distorted corner-sharing OCa2AlSi trigonal pyramids. In the sixteenth O site, O(16) is bonded to one Ca(2), one Ca(6), one Al(2), and one Si(5) atom to form distorted OCa2AlSi trigonal pyramids that share  a cornercorner with one O(12)Ca3Si trigonal pyramid,  an edgeedge with one O(6)Ca2Al2 trigonal pyramid, and  an edgeedge with one O(25)Ca2AlSi trigonal pyramid. In the seventeenth O site, O(17) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(6), and one Si(2) atom. In the eighteenth O site, O(18) is bonded in a distorted trigonal planar geometry to one Ca(6), one Mg(1), and one Si(1) atom. In the nineteenth O site, O(19) is bonded in a distorted T-shaped geometry to one Ca(4), one Mg(1), and one Si(5) atom. In the twentieth O site, O(20) is bonded in a 4-coordinate geometry to one Ca(7), one Ca(8), one Al(3), and one Si(2) atom. In the twenty-first O site, O(21) is bonded in a bent 150 degrees geometry to one Al(5) and one Si(1) atom. In the twenty-second O site, O(22) is bonded in a 4-coordinate geometry to one Ca(6), one Ca(7), one Al(3), and one Al(5) atom. In the twenty-third O site, O(23) is bonded in a 3-coordinate geometry to one Ca(5), one Al(1), and one Si(1) atom. In the twenty-fourth O site, O(24) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(4), one Al(2), and one Al(6) atom. In the twenty-fifth O site, O(25) is bonded to one Ca(2), one Ca(6), one Al(1), and one Si(2) atom to form distorted OCa2AlSi trigonal pyramids that share  a cornercorner with one O(6)Ca2Al2 trigonal pyramid,  a cornercorner with one O(12)Ca3Si trigonal pyramid, and  an edgeedge with one O(16)Ca2AlSi trigonal pyramid. In the twenty-sixth O site, O(26) is bonded in a 3-coordinate geometry to one Ca(8), one Al(4), and one Si(3) atom. In the twenty-seventh O site, O(27) is bonded in a distorted trigonal planar geometry to one Ca(7), one Al(2), and one Si(2) atom. In the twenty-eighth O site, O(28) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(3), one Al(2), and one Si(5) atom. is represented by the CIF file [CIF]
data_Ca8MgAl6Si5O28
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.512
_cell_length_b   9.054
_cell_length_c   9.383
_cell_angle_alpha   96.353
_cell_angle_beta   113.344
_cell_angle_gamma   102.427
_symmetry_Int_Tables_number   1
_cell_volume   632.712
_cell_formula_units_Z   1
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
loop_
 _atom_site_type_symbol
 _atom_site_label
 _atom_site_symmetry_multiplicity
 _atom_site_fract_x
 _atom_site_fract_y
 _atom_site_fract_z
 _atom_site_occupancy
  Ca  Ca0  1  0.486  0.177  0.226  1.0
  Ca  Ca1  1  0.683  0.543  0.891  1.0
  Ca  Ca2  1  0.364  0.176  0.821  1.0
  Ca  Ca3  1  0.187  0.340  0.375  1.0
  Ca  Ca4  1  0.920  0.240  0.893  1.0
  Ca  Ca5  1  0.830  0.912  0.208  1.0
  Ca  Ca6  1  0.189  0.655  0.160  1.0
  Ca  Ca7  1  0.983  0.666  0.702  1.0
  Mg  Mg8  1  0.923  0.251  0.523  1.0
  Al  Al9  1  0.693  0.874  0.825  1.0
  Al  Al10  1  0.521  0.503  0.123  1.0
  Al  Al11  1  0.100  0.941  0.014  1.0
  Al  Al12  1  0.225  0.458  0.749  1.0
  Al  Al13  1  0.326  0.972  0.416  1.0
  Al  Al14  1  0.533  0.583  0.445  1.0
  Si  Si15  1  0.723  0.924  0.521  1.0
  Si  Si16  1  0.443  0.811  0.032  1.0
  Si  Si17  1  0.367  0.744  0.607  1.0
  Si  Si18  1  0.573  0.293  0.585  1.0
  Si  Si19  1  0.827  0.436  0.198  1.0
  O  O20  1  0.268  0.885  0.556  1.0
  O  O21  1  0.729  0.737  0.505  1.0
  O  O22  1  0.024  0.433  0.770  1.0
  O  O23  1  0.575  0.479  0.602  1.0
  O  O24  1  0.882  0.786  0.895  1.0
  O  O25  1  0.415  0.447  0.909  1.0
  O  O26  1  0.946  0.446  0.093  1.0
  O  O27  1  0.221  0.106  0.977  1.0
  O  O28  1  0.187  0.290  0.611  1.0
  O  O29  1  0.328  0.624  0.431  1.0
  O  O30  1  0.694  0.261  0.499  1.0
  O  O31  1  0.620  0.269  0.766  1.0
  O  O32  1  0.984  0.086  0.095  1.0
  O  O33  1  0.785  0.051  0.996  1.0
  O  O34  1  0.370  0.178  0.451  1.0
  O  O35  1  0.767  0.603  0.193  1.0
  O  O36  1  0.560  0.979  0.144  1.0
  O  O37  1  0.861  0.017  0.457  1.0
  O  O38  1  0.933  0.388  0.363  1.0
  O  O39  1  0.224  0.800  0.948  1.0
  O  O40  1  0.515  0.922  0.423  1.0
  O  O41  1  0.165  0.900  0.216  1.0
  O  O42  1  0.787  0.995  0.711  1.0
  O  O43  1  0.449  0.438  0.269  1.0
  O  O44  1  0.571  0.774  0.941  1.0
  O  O45  1  0.238  0.629  0.670  1.0
  O  O46  1  0.444  0.674  0.136  1.0
  O  O47  1  0.620  0.324  0.103  1.0
[/CIF]
.
The compound described by Ca8MgAl6Si5O28 crystallizes in the triclinic P1 space group. There are eight inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 6-coordinate geometry to one O(11), one O(15), one O(17), one O(24), one O(28), and one O(8) atom. In the second Ca site, Ca(2) is bonded in a 7-coordinate geometry to one O(12), one O(16), one O(25), one O(4), one O(5), one O(6), and one O(7) atom. In the third Ca site, Ca(3) is bonded in a 5-coordinate geometry to one O(12), one O(28), one O(6), one O(8), and one O(9) atom. In the fourth Ca site, Ca(4) is bonded in a 8-coordinate geometry to one O(10), one O(13), one O(15), one O(19), one O(24), one O(4), one O(7), and one O(9) atom. In the fifth Ca site, Ca(5) is bonded to one O(12), one O(13), one O(14), one O(23), one O(3), one O(7), and one O(8) atom to form distorted CaO7 pentagonal bipyramids that share  a cornercorner with one Al(4)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra,  a cornercorner with one Si(5)O4 tetrahedra,  a cornercorner with one Ca(7)O5 trigonal bipyramid,  a cornercorner with one Mg(1)O5 trigonal bipyramid, and  an edgeedge with one Al(3)O5 trigonal bipyramid. In the sixth Ca site, Ca(6) is bonded in a 7-coordinate geometry to one O(13), one O(14), one O(16), one O(17), one O(18), one O(22), and one O(25) atom. In the seventh Ca site, Ca(7) is bonded to one O(10), one O(20), one O(22), one O(27), and one O(7) atom to form distorted CaO5 trigonal bipyramids that share  a cornercorner with one Ca(5)O7 pentagonal bipyramid,  a cornercorner with one Al(5)O4 tetrahedra,  a cornercorner with one Al(6)O4 tetrahedra,  a cornercorner with one Si(5)O4 tetrahedra,  a cornercorner with one Al(2)O5 trigonal bipyramid,  an edgeedge with one Si(2)O4 tetrahedra, and  an edgeedge with one Al(3)O5 trigonal bipyramid. In the eighth Ca site, Ca(8) is bonded in a distorted pentagonal planar geometry to one O(2), one O(20), one O(26), one O(3), and one O(5) atom. Mg(1) is bonded to one O(11), one O(18), one O(19), one O(3), and one O(9) atom to form distorted MgO5 trigonal bipyramids that share  a cornercorner with one Ca(5)O7 pentagonal bipyramid,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra,  a cornercorner with one Si(5)O4 tetrahedra, and  an edgeedge with one Al(4)O4 tetrahedra. There are six inequivalent Al sites. In the first Al site, Al(1) is bonded in a distorted rectangular see-saw-like geometry to one O(14), one O(23), one O(25), and one O(5) atom. In the second Al site, Al(2) is bonded to one O(16), one O(24), one O(27), one O(28), and one O(6) atom to form AlO5 trigonal bipyramids that share  a cornercorner with one Al(4)O4 tetrahedra,  a cornercorner with one Al(6)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Ca(7)O5 trigonal bipyramid, and  an edgeedge with one Si(5)O4 tetrahedra. In the third Al site, Al(3) is bonded to one O(13), one O(20), one O(22), one O(5), and one O(8) atom to form AlO5 trigonal bipyramids that share  a cornercorner with one Al(5)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra,  an edgeedge with one Ca(5)O7 pentagonal bipyramid, and  an edgeedge with one Ca(7)O5 trigonal bipyramid. In the fourth Al site, Al(4) is bonded to one O(26), one O(3), one O(6), and one O(9) atom to form AlO4 tetrahedra that share  a cornercorner with one Ca(5)O7 pentagonal bipyramid,  a cornercorner with one Al(2)O5 trigonal bipyramid, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. In the fifth Al site, Al(5) is bonded to one O(1), one O(15), one O(21), and one O(22) atom to form AlO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra,  a cornercorner with one Ca(7)O5 trigonal bipyramid, and  a cornercorner with one Al(3)O5 trigonal bipyramid. In the sixth Al site, Al(6) is bonded to one O(10), one O(2), one O(24), and one O(4) atom to form AlO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra,  a cornercorner with one Ca(7)O5 trigonal bipyramid, and  a cornercorner with one Al(2)O5 trigonal bipyramid. There are five inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(18), one O(2), one O(21), and one O(23) atom to form SiO4 tetrahedra that share  a cornercorner with one Ca(5)O7 pentagonal bipyramid,  a cornercorner with one Al(5)O4 tetrahedra,  a cornercorner with one Al(6)O4 tetrahedra, and  a cornercorner with one Mg(1)O5 trigonal bipyramid. In the second Si site, Si(2) is bonded to one O(17), one O(20), one O(25), and one O(27) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(2)O5 trigonal bipyramid,  a cornercorner with one Al(3)O5 trigonal bipyramid, and  an edgeedge with one Ca(7)O5 trigonal bipyramid. In the third Si site, Si(3) is bonded in a distorted trigonal non-coplanar geometry to one O(1), one O(10), and one O(26) atom. In the fourth Si site, Si(4) is bonded to one O(11), one O(12), one O(15), and one O(4) atom to form SiO4 tetrahedra that share  a cornercorner with one Ca(5)O7 pentagonal bipyramid,  a cornercorner with one Al(5)O4 tetrahedra,  a cornercorner with one Al(6)O4 tetrahedra, and  a cornercorner with one Mg(1)O5 trigonal bipyramid. In the fifth Si site, Si(5) is bonded to one O(16), one O(19), one O(28), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Ca(5)O7 pentagonal bipyramid,  a cornercorner with one Ca(7)O5 trigonal bipyramid,  a cornercorner with one Mg(1)O5 trigonal bipyramid, and  an edgeedge with one Al(2)O5 trigonal bipyramid. There are twenty-eight inequivalent O sites. In the first O site, O(1) is bonded in a water-like geometry to one Al(5) and one Si(3) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Ca(8), one Al(6), and one Si(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ca(5), one Ca(8), one Mg(1), and one Al(4) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Ca(2), one Ca(4), one Al(6), and one Si(4) atom. In the fifth O site, O(5) is bonded in a distorted see-saw-like geometry to one Ca(2), one Ca(8), one Al(1), and one Al(3) atom. In the sixth O site, O(6) is bonded to one Ca(2), one Ca(3), one Al(2), and one Al(4) atom to form distorted OCa2Al2 trigonal pyramids that share  a cornercorner with one O(25)Ca2AlSi trigonal pyramid,  an edgeedge with one O(16)Ca2AlSi trigonal pyramid, and  an edgeedge with one O(12)Ca3Si trigonal pyramid. In the seventh O site, O(7) is bonded in a 5-coordinate geometry to one Ca(2), one Ca(4), one Ca(5), one Ca(7), and one Si(5) atom. In the eighth O site, O(8) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(3), one Ca(5), and one Al(3) atom. In the ninth O site, O(9) is bonded in a distorted rectangular see-saw-like geometry to one Ca(3), one Ca(4), one Mg(1), and one Al(4) atom. In the tenth O site, O(10) is bonded in a distorted rectangular see-saw-like geometry to one Ca(4), one Ca(7), one Al(6), and one Si(3) atom. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to one Ca(1), one Mg(1), and one Si(4) atom. In the twelfth O site, O(12) is bonded to one Ca(2), one Ca(3), one Ca(5), and one Si(4) atom to form distorted OCa3Si trigonal pyramids that share  a cornercorner with one O(15)Ca2AlSi trigonal pyramid,  a cornercorner with one O(16)Ca2AlSi trigonal pyramid,  a cornercorner with one O(25)Ca2AlSi trigonal pyramid, and  an edgeedge with one O(6)Ca2Al2 trigonal pyramid. In the thirteenth O site, O(13) is bonded in a 5-coordinate geometry to one Ca(4), one Ca(5), one Ca(6), one Al(3), and one O(14) atom. In the fourteenth O site, O(14) is bonded in a 4-coordinate geometry to one Ca(5), one Ca(6), one Al(1), and one O(13) atom. In the fifteenth O site, O(15) is bonded to one Ca(1), one Ca(4), one Al(5), and one Si(4) atom to form distorted corner-sharing OCa2AlSi trigonal pyramids. In the sixteenth O site, O(16) is bonded to one Ca(2), one Ca(6), one Al(2), and one Si(5) atom to form distorted OCa2AlSi trigonal pyramids that share  a cornercorner with one O(12)Ca3Si trigonal pyramid,  an edgeedge with one O(6)Ca2Al2 trigonal pyramid, and  an edgeedge with one O(25)Ca2AlSi trigonal pyramid. In the seventeenth O site, O(17) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(6), and one Si(2) atom. In the eighteenth O site, O(18) is bonded in a distorted trigonal planar geometry to one Ca(6), one Mg(1), and one Si(1) atom. In the nineteenth O site, O(19) is bonded in a distorted T-shaped geometry to one Ca(4), one Mg(1), and one Si(5) atom. In the twentieth O site, O(20) is bonded in a 4-coordinate geometry to one Ca(7), one Ca(8), one Al(3), and one Si(2) atom. In the twenty-first O site, O(21) is bonded in a bent 150 degrees geometry to one Al(5) and one Si(1) atom. In the twenty-second O site, O(22) is bonded in a 4-coordinate geometry to one Ca(6), one Ca(7), one Al(3), and one Al(5) atom. In the twenty-third O site, O(23) is bonded in a 3-coordinate geometry to one Ca(5), one Al(1), and one Si(1) atom. In the twenty-fourth O site, O(24) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(4), one Al(2), and one Al(6) atom. In the twenty-fifth O site, O(25) is bonded to one Ca(2), one Ca(6), one Al(1), and one Si(2) atom to form distorted OCa2AlSi trigonal pyramids that share  a cornercorner with one O(6)Ca2Al2 trigonal pyramid,  a cornercorner with one O(12)Ca3Si trigonal pyramid, and  an edgeedge with one O(16)Ca2AlSi trigonal pyramid. In the twenty-sixth O site, O(26) is bonded in a 3-coordinate geometry to one Ca(8), one Al(4), and one Si(3) atom. In the twenty-seventh O site, O(27) is bonded in a distorted trigonal planar geometry to one Ca(7), one Al(2), and one Si(2) atom. In the twenty-eighth O site, O(28) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(3), one Al(2), and one Si(5) atom. is represented by the CIF file [CIF]
data_Ca8MgAl6Si5O28
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.512
_cell_length_b   9.054
_cell_length_c   9.383
_cell_angle_alpha   96.353
_cell_angle_beta   113.344
_cell_angle_gamma   102.427
_symmetry_Int_Tables_number   1
_cell_volume   632.712
_cell_formula_units_Z   1
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
loop_
 _atom_site_type_symbol
 _atom_site_label
 _atom_site_symmetry_multiplicity
 _atom_site_fract_x
 _atom_site_fract_y
 _atom_site_fract_z
 _atom_site_occupancy
  Ca  Ca0  1  0.486  0.177  0.226  1.0
  Ca  Ca1  1  0.683  0.543  0.891  1.0
  Ca  Ca2  1  0.364  0.176  0.821  1.0
  Ca  Ca3  1  0.187  0.340  0.375  1.0
  Ca  Ca4  1  0.920  0.240  0.893  1.0
  Ca  Ca5  1  0.830  0.912  0.208  1.0
  Ca  Ca6  1  0.189  0.655  0.160  1.0
  Ca  Ca7  1  0.983  0.666  0.702  1.0
  Mg  Mg8  1  0.923  0.251  0.523  1.0
  Al  Al9  1  0.693  0.874  0.825  1.0
  Al  Al10  1  0.521  0.503  0.123  1.0
  Al  Al11  1  0.100  0.941  0.014  1.0
  Al  Al12  1  0.225  0.458  0.749  1.0
  Al  Al13  1  0.326  0.972  0.416  1.0
  Al  Al14  1  0.533  0.583  0.445  1.0
  Si  Si15  1  0.723  0.924  0.521  1.0
  Si  Si16  1  0.443  0.811  0.032  1.0
  Si  Si17  1  0.367  0.744  0.607  1.0
  Si  Si18  1  0.573  0.293  0.585  1.0
  Si  Si19  1  0.827  0.436  0.198  1.0
  O  O20  1  0.268  0.885  0.556  1.0
  O  O21  1  0.729  0.737  0.505  1.0
  O  O22  1  0.024  0.433  0.770  1.0
  O  O23  1  0.575  0.479  0.602  1.0
  O  O24  1  0.882  0.786  0.895  1.0
  O  O25  1  0.415  0.447  0.909  1.0
  O  O26  1  0.946  0.446  0.093  1.0
  O  O27  1  0.221  0.106  0.977  1.0
  O  O28  1  0.187  0.290  0.611  1.0
  O  O29  1  0.328  0.624  0.431  1.0
  O  O30  1  0.694  0.261  0.499  1.0
  O  O31  1  0.620  0.269  0.766  1.0
  O  O32  1  0.984  0.086  0.095  1.0
  O  O33  1  0.785  0.051  0.996  1.0
  O  O34  1  0.370  0.178  0.451  1.0
  O  O35  1  0.767  0.603  0.193  1.0
  O  O36  1  0.560  0.979  0.144  1.0
  O  O37  1  0.861  0.017  0.457  1.0
  O  O38  1  0.933  0.388  0.363  1.0
  O  O39  1  0.224  0.800  0.948  1.0
  O  O40  1  0.515  0.922  0.423  1.0
  O  O41  1  0.165  0.900  0.216  1.0
  O  O42  1  0.787  0.995  0.711  1.0
  O  O43  1  0.449  0.438  0.269  1.0
  O  O44  1  0.571  0.774  0.941  1.0
  O  O45  1  0.238  0.629  0.670  1.0
  O  O46  1  0.444  0.674  0.136  1.0
  O  O47  1  0.620  0.324  0.103  1.0
[/CIF]
.