RbAlSi3O8 crystallizes in the triclinic P-1 space group. Rb(1) is bonded in a 10-coordinate geometry to one O(2), one O(3), one O(4), one O(5), one O(6), one O(7), two equivalent O(1), and two equivalent O(8) atoms. Al(1) is bonded to one O(2), one O(4), 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(2)O4 tetrahedra, and corners with two equivalent Si(3)O4 tetrahedra. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(3), one O(5), one O(7), and one O(8) 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(2)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(5), and one O(6) 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. In the third Si site, Si(3) is bonded to one O(1), one O(2), one O(4), and one O(7) 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. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to two equivalent Rb(1), one Si(2), and one Si(3) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Rb(1), one Al(1), and one Si(3) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Rb(1), one Si(1), and one Si(2) atom. In the fourth O site, O(4) is bonded in a distorted bent 120 degrees geometry to one Rb(1), one Al(1), and one Si(3) atom. In the fifth O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Rb(1), one Si(1), and one Si(2) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Rb(1), one Al(1), and one Si(2) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Rb(1), one Si(1), and one Si(3) atom. In the eighth O site, O(8) is bonded in a distorted bent 150 degrees geometry to two equivalent Rb(1), one Al(1), and one Si(1) atom.
RbAlSi3O8 crystallizes in the triclinic P-1 space group. Rb(1) is bonded in a 10-coordinate geometry to one O(2), one O(3), one O(4), one O(5), one O(6), one O(7), two equivalent O(1), and two equivalent O(8) atoms. The Rb(1)-O(2) bond length is 3.00 Å. The Rb(1)-O(3) bond length is 3.18 Å. The Rb(1)-O(4) bond length is 3.03 Å. The Rb(1)-O(5) bond length is 3.27 Å. The Rb(1)-O(6) bond length is 3.17 Å. The Rb(1)-O(7) bond length is 3.29 Å. There is one shorter (3.04 Å) and one longer (3.33 Å) Rb(1)-O(1) bond length. There is one shorter (3.08 Å) and one longer (3.13 Å) Rb(1)-O(8) bond length. Al(1) is bonded to one O(2), one O(4), 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(2)O4 tetrahedra, and corners with two equivalent Si(3)O4 tetrahedra. The Al(1)-O(2) bond length is 1.76 Å. The Al(1)-O(4) 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 1.76 Å. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(3), one O(5), one O(7), and one O(8) 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(2)O4 tetrahedra. The Si(1)-O(3) bond length is 1.65 Å. The Si(1)-O(5) bond length is 1.65 Å. The Si(1)-O(7) bond length is 1.63 Å. The Si(1)-O(8) bond length is 1.61 Å. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(5), and one O(6) 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(2)-O(1) bond length is 1.64 Å. The Si(2)-O(3) bond length is 1.65 Å. The Si(2)-O(5) bond length is 1.65 Å. The Si(2)-O(6) bond length is 1.60 Å. In the third Si site, Si(3) is bonded to one O(1), one O(2), one O(4), and one O(7) 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(3)-O(1) bond length is 1.66 Å. The Si(3)-O(2) bond length is 1.61 Å. The Si(3)-O(4) bond length is 1.62 Å. The Si(3)-O(7) bond length is 1.65 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to two equivalent Rb(1), one Si(2), and one Si(3) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Rb(1), one Al(1), and one Si(3) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Rb(1), one Si(1), and one Si(2) atom. In the fourth O site, O(4) is bonded in a distorted bent 120 degrees geometry to one Rb(1), one Al(1), and one Si(3) atom. In the fifth O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Rb(1), one Si(1), and one Si(2) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Rb(1), one Al(1), and one Si(2) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Rb(1), one Si(1), and one Si(3) atom. In the eighth O site, O(8) is bonded in a distorted bent 150 degrees geometry to two equivalent Rb(1), one Al(1), and one Si(1) atom.