In geometry, the sphenocorona is a Johnson solid with 12 equilateral triangles and 2 squares as its faces.

The sphenocorona was named by Johnson (1966) in which he used the prefix spheno- referring to a wedge-like complex formed by two adjacent lunes—a square with equilateral triangles attached on its opposite sides.

The suffix -corona refers to a crownlike complex of 8 equilateral triangles.

[1] By joining both complexes together, the resulting polyhedron has 12 equilateral triangles and 2 squares, making 14 faces.

[2] A convex polyhedron in which all faces are regular polygons is called a Johnson solid.

The sphenocorona is among them, enumerated as the 86th Johnson solid

{\displaystyle J_{86}}

.

[3] It is an elementary polyhedron, meaning it cannot be separated by a plane into two small regular-faced polyhedra.

[4] The surface area of a sphenocorona with edge length

a

{\displaystyle a}

can be calculated as:[2]

and its volume as:[2]

be the smallest positive root of the quartic polynomial

Then, Cartesian coordinates of a sphenocorona with edge length 2 are given by the union of the orbits of the points

under the action of the group generated by reflections about the xz-plane and the yz-plane.

[5] The sphenocorona is also the vertex figure of the isogonal n-gonal double antiprismoid where n is an odd number greater than one, including the grand antiprism with pairs of trapezoid rather than square faces.