The structure described by Ca2MgAl2(SiO4)3 is Esseneite-derived structured and crystallizes in the triclinic P-1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 8-coordinate geometry to one O(1), one O(3), one O(4), one O(5), one O(7), one O(8), and two equivalent O(6) atoms. In the second Ca site, Ca(2) is bonded in a 8-coordinate geometry to one O(1), one O(10), one O(11), one O(2), one O(7), one O(9), and two equivalent O(12) atoms. Mg(1) is bonded to one O(10), one O(2), one O(4), one O(5), and two equivalent O(3) atoms to form MgO6 octahedra that share  a cornercorner with one Si(3)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, corners with three equivalent Si(1)O4 tetrahedra,  an edgeedge with one Mg(1)O6 octahedra, and  an edgeedge with one Al(2)O6 octahedra. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(12), one O(7), one O(8), and one O(9) atom to form AlO4 tetrahedra that share corners with three equivalent Al(2)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 33-62°. In the second Al site, Al(2) is bonded to one O(10), one O(11), one O(4), one O(8), and two equivalent O(9) atoms to form AlO6 octahedra that share  a cornercorner with one Si(2)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra, corners with three equivalent Al(1)O4 tetrahedra,  an edgeedge with one Mg(1)O6 octahedra, and  an edgeedge with one Al(2)O6 octahedra. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(3), and one O(6) atom to form SiO4 tetrahedra that share corners with three equivalent Mg(1)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 38-59°. In the second Si site, Si(2) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(2)O6 octahedra, corners with two equivalent Mg(1)O6 octahedra,  a cornercorner with one Al(1)O4 tetrahedra, and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 41-60°. In the third Si site, Si(3) is bonded to one O(1), one O(10), one O(11), and one O(12) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra, corners with two equivalent Al(2)O6 octahedra,  a cornercorner with one Al(1)O4 tetrahedra, and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 34-62°. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Ca(1), one Ca(2), one Si(1), and one Si(3) atom. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Ca(2), one Mg(1), and one Si(1) atom. In the third O site, O(3) is bonded to one Ca(1), two equivalent Mg(1), and one Si(1) atom to form distorted edge-sharing OCaMg2Si tetrahedra. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Ca(1), one Mg(1), one Al(2), and one Si(2) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Ca(1), one Mg(1), and one Si(2) atom. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to two equivalent Ca(1), one Si(1), and one Si(2) atom. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Al(1), and one Si(2) atom. In the eighth O site, O(8) is bonded in a distorted T-shaped geometry to one Ca(1), one Al(1), and one Al(2) atom. In the ninth O site, O(9) is bonded to one Ca(2), one Al(1), and two equivalent Al(2) atoms to form distorted edge-sharing OCaAl3 tetrahedra. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one Ca(2), one Mg(1), one Al(2), and one Si(3) atom. In the eleventh O site, O(11) is bonded in a distorted T-shaped geometry to one Ca(2), one Al(2), and one Si(3) atom. In the twelfth O site, O(12) is bonded in a 4-coordinate geometry to two equivalent Ca(2), one Al(1), and one Si(3) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ca2MgAl2(SiO4)3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.594
_cell_length_b   6.616
_cell_length_c   10.650
_cell_angle_alpha   78.353
_cell_angle_beta   77.590
_cell_angle_gamma   84.051
_symmetry_Int_Tables_number   1
_cell_volume   443.522
_cell_formula_units_Z   2
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  0.697  0.300  0.871  1.0
  Ca  Ca1  1  0.303  0.700  0.129  1.0
  Ca  Ca2  1  0.691  0.309  0.377  1.0
  Ca  Ca3  1  0.309  0.691  0.623  1.0
  Mg  Mg4  1  0.095  0.906  0.875  1.0
  Mg  Mg5  1  0.905  0.094  0.125  1.0
  Al  Al6  1  0.187  0.387  0.391  1.0
  Al  Al7  1  0.091  0.912  0.379  1.0
  Al  Al8  1  0.909  0.088  0.621  1.0
  Al  Al9  1  0.813  0.613  0.609  1.0
  Si  Si10  1  0.192  0.376  0.886  1.0
  Si  Si11  1  0.620  0.803  0.861  1.0
  Si  Si12  1  0.380  0.197  0.139  1.0
  Si  Si13  1  0.808  0.624  0.114  1.0
  Si  Si14  1  0.615  0.810  0.363  1.0
  Si  Si15  1  0.385  0.190  0.637  1.0
  O  O16  1  0.376  0.319  0.758  1.0
  O  O17  1  0.112  0.611  0.835  1.0
  O  O18  1  0.023  0.202  0.931  1.0
  O  O19  1  0.805  0.969  0.807  1.0
  O  O20  1  0.389  0.894  0.913  1.0
  O  O21  1  0.326  0.367  0.004  1.0
  O  O22  1  0.674  0.633  0.996  1.0
  O  O23  1  0.611  0.106  0.087  1.0
  O  O24  1  0.195  0.031  0.193  1.0
  O  O25  1  0.977  0.798  0.069  1.0
  O  O26  1  0.888  0.389  0.165  1.0
  O  O27  1  0.375  0.344  0.247  1.0
  O  O28  1  0.624  0.681  0.242  1.0
  O  O29  1  0.109  0.647  0.345  1.0
  O  O30  1  0.021  0.180  0.437  1.0
  O  O31  1  0.800  0.973  0.323  1.0
  O  O32  1  0.376  0.899  0.407  1.0
  O  O33  1  0.342  0.370  0.511  1.0
  O  O34  1  0.658  0.630  0.489  1.0
  O  O35  1  0.624  0.101  0.593  1.0
  O  O36  1  0.200  0.027  0.677  1.0
  O  O37  1  0.979  0.820  0.563  1.0
  O  O38  1  0.891  0.353  0.655  1.0
  O  O39  1  0.625  0.656  0.753  1.0
[/CIF]
.
The structure described by Ca2MgAl2(SiO4)3 is Esseneite-derived structured and crystallizes in the triclinic P-1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 8-coordinate geometry to one O(1), one O(3), one O(4), one O(5), one O(7), one O(8), and two equivalent O(6) atoms. In the second Ca site, Ca(2) is bonded in a 8-coordinate geometry to one O(1), one O(10), one O(11), one O(2), one O(7), one O(9), and two equivalent O(12) atoms. Mg(1) is bonded to one O(10), one O(2), one O(4), one O(5), and two equivalent O(3) atoms to form MgO6 octahedra that share  a cornercorner with one Si(3)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, corners with three equivalent Si(1)O4 tetrahedra,  an edgeedge with one Mg(1)O6 octahedra, and  an edgeedge with one Al(2)O6 octahedra. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(12), one O(7), one O(8), and one O(9) atom to form AlO4 tetrahedra that share corners with three equivalent Al(2)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 33-62°. In the second Al site, Al(2) is bonded to one O(10), one O(11), one O(4), one O(8), and two equivalent O(9) atoms to form AlO6 octahedra that share  a cornercorner with one Si(2)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra, corners with three equivalent Al(1)O4 tetrahedra,  an edgeedge with one Mg(1)O6 octahedra, and  an edgeedge with one Al(2)O6 octahedra. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(3), and one O(6) atom to form SiO4 tetrahedra that share corners with three equivalent Mg(1)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 38-59°. In the second Si site, Si(2) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(2)O6 octahedra, corners with two equivalent Mg(1)O6 octahedra,  a cornercorner with one Al(1)O4 tetrahedra, and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 41-60°. In the third Si site, Si(3) is bonded to one O(1), one O(10), one O(11), and one O(12) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra, corners with two equivalent Al(2)O6 octahedra,  a cornercorner with one Al(1)O4 tetrahedra, and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 34-62°. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Ca(1), one Ca(2), one Si(1), and one Si(3) atom. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Ca(2), one Mg(1), and one Si(1) atom. In the third O site, O(3) is bonded to one Ca(1), two equivalent Mg(1), and one Si(1) atom to form distorted edge-sharing OCaMg2Si tetrahedra. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Ca(1), one Mg(1), one Al(2), and one Si(2) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Ca(1), one Mg(1), and one Si(2) atom. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to two equivalent Ca(1), one Si(1), and one Si(2) atom. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Al(1), and one Si(2) atom. In the eighth O site, O(8) is bonded in a distorted T-shaped geometry to one Ca(1), one Al(1), and one Al(2) atom. In the ninth O site, O(9) is bonded to one Ca(2), one Al(1), and two equivalent Al(2) atoms to form distorted edge-sharing OCaAl3 tetrahedra. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one Ca(2), one Mg(1), one Al(2), and one Si(3) atom. In the eleventh O site, O(11) is bonded in a distorted T-shaped geometry to one Ca(2), one Al(2), and one Si(3) atom. In the twelfth O site, O(12) is bonded in a 4-coordinate geometry to two equivalent Ca(2), one Al(1), and one Si(3) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ca2MgAl2(SiO4)3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.594
_cell_length_b   6.616
_cell_length_c   10.650
_cell_angle_alpha   78.353
_cell_angle_beta   77.590
_cell_angle_gamma   84.051
_symmetry_Int_Tables_number   1
_cell_volume   443.522
_cell_formula_units_Z   2
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  0.697  0.300  0.871  1.0
  Ca  Ca1  1  0.303  0.700  0.129  1.0
  Ca  Ca2  1  0.691  0.309  0.377  1.0
  Ca  Ca3  1  0.309  0.691  0.623  1.0
  Mg  Mg4  1  0.095  0.906  0.875  1.0
  Mg  Mg5  1  0.905  0.094  0.125  1.0
  Al  Al6  1  0.187  0.387  0.391  1.0
  Al  Al7  1  0.091  0.912  0.379  1.0
  Al  Al8  1  0.909  0.088  0.621  1.0
  Al  Al9  1  0.813  0.613  0.609  1.0
  Si  Si10  1  0.192  0.376  0.886  1.0
  Si  Si11  1  0.620  0.803  0.861  1.0
  Si  Si12  1  0.380  0.197  0.139  1.0
  Si  Si13  1  0.808  0.624  0.114  1.0
  Si  Si14  1  0.615  0.810  0.363  1.0
  Si  Si15  1  0.385  0.190  0.637  1.0
  O  O16  1  0.376  0.319  0.758  1.0
  O  O17  1  0.112  0.611  0.835  1.0
  O  O18  1  0.023  0.202  0.931  1.0
  O  O19  1  0.805  0.969  0.807  1.0
  O  O20  1  0.389  0.894  0.913  1.0
  O  O21  1  0.326  0.367  0.004  1.0
  O  O22  1  0.674  0.633  0.996  1.0
  O  O23  1  0.611  0.106  0.087  1.0
  O  O24  1  0.195  0.031  0.193  1.0
  O  O25  1  0.977  0.798  0.069  1.0
  O  O26  1  0.888  0.389  0.165  1.0
  O  O27  1  0.375  0.344  0.247  1.0
  O  O28  1  0.624  0.681  0.242  1.0
  O  O29  1  0.109  0.647  0.345  1.0
  O  O30  1  0.021  0.180  0.437  1.0
  O  O31  1  0.800  0.973  0.323  1.0
  O  O32  1  0.376  0.899  0.407  1.0
  O  O33  1  0.342  0.370  0.511  1.0
  O  O34  1  0.658  0.630  0.489  1.0
  O  O35  1  0.624  0.101  0.593  1.0
  O  O36  1  0.200  0.027  0.677  1.0
  O  O37  1  0.979  0.820  0.563  1.0
  O  O38  1  0.891  0.353  0.655  1.0
  O  O39  1  0.625  0.656  0.753  1.0
[/CIF]
.