KAlSi3O8 crystallizes in the monoclinic C2 space group. K(1) is bonded in a 10-coordinate geometry to one O(1), one O(2), one O(4), one O(5), one O(6), one O(7), one O(8), one O(9), and two equivalent O(3) atoms. Al(1) is bonded to one O(3), one O(5), one O(6), and one O(8) atom to form AlO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and corners with two equivalent Si(2)O4 tetrahedra. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(3), one O(4), one O(7), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Si(3)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(1), one O(4), one O(6), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Al(1)O4 tetrahedra. In the third Si site, Si(3) is bonded to one O(2), one O(5), one O(7), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and corners with two equivalent Si(1)O4 tetrahedra. There are nine inequivalent O sites. In the first O site, O(8) is bonded in a bent 150 degrees geometry to one K(1), one Al(1), and one Si(2) atom. In the second O site, O(9) is bonded in a bent 150 degrees geometry to one K(1), one Si(1), and one Si(3) atom. In the third O site, O(1) is bonded in a bent 150 degrees geometry to two equivalent K(1) and two equivalent Si(2) atoms. In the fourth O site, O(2) is bonded in a distorted bent 150 degrees geometry to two equivalent K(1) and two equivalent Si(3) atoms. In the fifth O site, O(3) is bonded in a 2-coordinate geometry to two equivalent K(1), one Al(1), and one Si(1) atom. In the sixth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one K(1), one Si(1), and one Si(2) atom. In the seventh O site, O(5) is bonded in a distorted bent 120 degrees geometry to one K(1), one Al(1), and one Si(3) atom. In the eighth O site, O(6) is bonded in a 2-coordinate geometry to one K(1), one Al(1), and one Si(2) atom. In the ninth O site, O(7) is bonded in a distorted bent 150 degrees geometry to one K(1), one Si(1), and one Si(3) atom.
KAlSi3O8 crystallizes in the monoclinic C2 space group. K(1) is bonded in a 10-coordinate geometry to one O(1), one O(2), one O(4), one O(5), one O(6), one O(7), one O(8), one O(9), and two equivalent O(3) atoms. The K(1)-O(1) bond length is 3.00 Å. The K(1)-O(2) bond length is 3.05 Å. The K(1)-O(4) bond length is 3.35 Å. The K(1)-O(5) bond length is 3.10 Å. The K(1)-O(6) bond length is 2.87 Å. The K(1)-O(7) bond length is 3.10 Å. The K(1)-O(8) bond length is 3.06 Å. The K(1)-O(9) bond length is 3.12 Å. There is one shorter (2.78 Å) and one longer (3.38 Å) K(1)-O(3) bond length. Al(1) is bonded to one O(3), one O(5), one O(6), and one O(8) atom to form AlO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and corners with two equivalent Si(2)O4 tetrahedra. The Al(1)-O(3) bond length is 1.76 Å. The Al(1)-O(5) bond length is 1.76 Å. The Al(1)-O(6) bond length is 1.75 Å. The Al(1)-O(8) bond length is 1.74 Å. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(3), one O(4), one O(7), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Si(3)O4 tetrahedra. The Si(1)-O(3) bond length is 1.61 Å. The Si(1)-O(4) bond length is 1.64 Å. The Si(1)-O(7) bond length is 1.65 Å. The Si(1)-O(9) bond length is 1.64 Å. In the second Si site, Si(2) is bonded to one O(1), one O(4), one O(6), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Al(1)O4 tetrahedra. The Si(2)-O(1) bond length is 1.64 Å. The Si(2)-O(4) bond length is 1.65 Å. The Si(2)-O(6) bond length is 1.61 Å. The Si(2)-O(8) bond length is 1.61 Å. In the third Si site, Si(3) is bonded to one O(2), one O(5), one O(7), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and corners with two equivalent Si(1)O4 tetrahedra. The Si(3)-O(2) bond length is 1.66 Å. The Si(3)-O(5) bond length is 1.60 Å. The Si(3)-O(7) bond length is 1.66 Å. The Si(3)-O(9) bond length is 1.64 Å. There are nine inequivalent O sites. In the first O site, O(8) is bonded in a bent 150 degrees geometry to one K(1), one Al(1), and one Si(2) atom. In the second O site, O(9) is bonded in a bent 150 degrees geometry to one K(1), one Si(1), and one Si(3) atom. In the third O site, O(1) is bonded in a bent 150 degrees geometry to two equivalent K(1) and two equivalent Si(2) atoms. In the fourth O site, O(2) is bonded in a distorted bent 150 degrees geometry to two equivalent K(1) and two equivalent Si(3) atoms. In the fifth O site, O(3) is bonded in a 2-coordinate geometry to two equivalent K(1), one Al(1), and one Si(1) atom. In the sixth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one K(1), one Si(1), and one Si(2) atom. In the seventh O site, O(5) is bonded in a distorted bent 120 degrees geometry to one K(1), one Al(1), and one Si(3) atom. In the eighth O site, O(6) is bonded in a 2-coordinate geometry to one K(1), one Al(1), and one Si(2) atom. In the ninth O site, O(7) is bonded in a distorted bent 150 degrees geometry to one K(1), one Si(1), and one Si(3) atom.