Johnson solid

The elongated square gyrobicupola (J37), a Johnson solid
This 24 equilateral triangle example is not a Johnson solid because it is not convex.
This 24-square example is not a Johnson solid because it is not strictly convex (has 180° dihedral angles.)

In geometry, a Johnson solid is a strictly convex polyhedron, which is not uniform (i.e., not a Platonic solid, Archimedean solid, prism, or antiprism), and each face of which is a regular polygon. There is no requirement that each face must be the same polygon, or that the same polygons join around each vertex. An example of a Johnson solid is the square-based pyramid with equilateral sides (J1); it has 1 square face and 4 triangular faces.

As in any strictly convex solid, at least three faces meet at every vertex, and the total of their angles is less than 360 degrees. Since a regular polygon has angles at least 60 degrees, it follows that at most five faces meet at any vertex. The pentagonal pyramid (J2) is an example that actually has a degree-5 vertex.

Although there is no obvious restriction that any given regular polygon cannot be a face of a Johnson solid, it turns out that the faces of Johnson solids always have 3, 4, 5, 6, 8, or 10 sides.

In 1966, Norman Johnson published a list which included all 92 solids, and gave them their names and numbers. He did not prove that there were only 92, but he did conjecture that there were no others. Victor Zalgaller in 1969 proved that Johnson's list was complete.

Of the Johnson solids, the elongated square gyrobicupola (J37), also called the pseudorhombicuboctahedron,[1] is unique in being locally vertex-uniform: there are 4 faces at each vertex, and their arrangement is always the same: 3 squares and 1 triangle. However, it is not vertex-transitive, as it has different isometry at different vertices, making it a Johnson solid rather than an Archimedean solid.

Names

The naming of Johnson solids follows a flexible and precise descriptive formula, such that many solids can be named in different ways without compromising their accuracy as a description. Most Johnson solids can be constructed from the first few (pyramids, cupolae, and rotunda), together with the Platonic and Archimedean solids, prisms, and antiprisms; the centre of a particular solid's name will reflect these ingredients. From there, a series of prefixes are attached to the word to indicate additions, rotations and transformations:

• Bi- indicates that two copies of the solid in question are joined base-to-base. For cupolae and rotundae, the solids can be joined so that either like faces (ortho-) or unlike faces (gyro-) meet. Using this nomenclature, an octahedron can be described as a square bipyramid, a cuboctahedron as a triangular gyrobicupola, and an icosidodecahedron as a pentagonal gyrobirotunda.
• Elongated indicates a prism is joined to the base of the solid in question, or between the bases in the case of Bi- solids. A rhombicuboctahedron can thus be described as an elongated square orthobicupola.
• Gyroelongated indicates an antiprism is joined to the base of the solid in question or between the bases in the case of Bi- solids. An icosahedron can thus be described as a gyroelongated pentagonal bipyramid.
• Augmented indicates another polyhedron, namely a pyramid or cupola, is joined to one or more faces of the solid in question.
• Diminished indicates a pyramid or cupola is removed from one or more faces of the solid in question.
• Gyrate indicates a cupola mounted on or featured in the solid in question is rotated such that different edges match up, as in the difference between ortho- and gyrobicupolae.

The last three operations – augmentation, diminution, and gyration – can be performed multiple times for certain large solids. Bi- & Tri- indicate a double and triple operation respectively. For example, a bigyrate solid has two rotated cupolae, and a tridiminished solid has three removed pyramids or cupolae.

In certain large solids, a distinction is made between solids where altered faces are parallel and solids where altered faces are oblique. Para- indicates the former, that the solid in question has altered parallel faces, and Meta- the latter, altered oblique faces. For example, a parabiaugmented solid has had two parallel faces augmented, and a metabigyrate solid has had 2 oblique faces gyrated.

The last few Johnson solids have names based on certain polygon complexes from which they are assembled. These names are defined by Johnson[2] with the following nomenclature:

• A lune is a complex of two triangles attached to opposite sides of a square.
• Spheno- indicates a wedgelike complex formed by two adjacent lunes. Dispheno- indicates two such complexes.
• Hebespheno- indicates a blunt complex of two lunes separated by a third lune.
• Corona is a crownlike complex of eight triangles.
• Megacorona is a larger crownlike complex of 12 triangles.
• The suffix -cingulum indicates a belt of 12 triangles.

Enumeration

Pyramids, cupolae and rotundae

The first 6 Johnson solids are pyramids, cupolae, or rotundae with at most 5 sides. 6 sided pyramids and cupolae are coplanar and are hence not Johnson solids.

Pyramids

The first two Johnson solids, J1 and J2, are pyramids. The triangular pyramid is the regular tetrahedron, so it is not a Johnson solid.

Regular J1 J2
Triangular pyramid
(Tetrahedron)
Square pyramid Pentagonal pyramid

Cupolae and rotunda

The next four Johnson solids are three cupolae and one rotunda. They represent sections of uniform polyhedra.

Cupola Rotunda
Uniform J3 J4 J5 J6
Fastigium
(Triangular prism)
Triangular cupola Square cupola Pentagonal cupola Pentagonal rotunda

Related uniform polyhedra
Cuboctahedron Rhombicuboctahedron Rhombicosidodecahedron Icosidodecahedron

Modified pyramids, cupolae and rotundae

Johnson solids 7 to 48 are derived from pyramids, cupolae and rotundae.

Elongated and gyroelongated pyramids

In the gyroelongated triangular pyramid, three pairs of adjacent triangles are coplanar and form non-square rhombi, so it is not a Johnson solid.

Elongated pyramids Gyroelongated pyramids
J7 J8 J9 Coplanar J10 J11
Elongated triangular pyramid Elongated square pyramid Elongated pentagonal pyramid Gyroelongated triangular pyramid
(diminished trigonal trapezohedron)
Gyroelongated square pyramid Gyroelongated pentagonal pyramid

Augmented from polyhedra
tetrahedron
triangular prism
square pyramid
cube
pentagonal pyramid
pentagonal prism
tetrahedron
octahedron
square pyramid
square antiprism
pentagonal pyramid
pentagonal antiprism

Bipyramids

The square bipyramid is the regular octahedron, while the gyroelongated pentagonal bipyramid is the regular icosahedron, so they are not Johnson solids. In the gyroelongated triangular bipyramid, six pairs of adjacent triangles are coplanar and form non-square rhombi, so it is also not a Johnson solid.

Bipyramids Elongated bipyramids Gyroelongated bipyramids
J12 Regular J13 J14 J15 J16 Coplanar J17 Regular
Triangular bipyramid Square bipyramid
(octahedron)
Pentagonal bipyramid Elongated triangular bipyramid Elongated square bipyramid Elongated pentagonal bipyramid Gyroelongated triangular bipyramid
(trigonal trapezohedron(rhombohedron))
Gyroelongated square bipyramid Gyroelongated pentagonal bipyramid
(icosahedron)

Augmented from polyhedra
tetrahedron square pyramid pentagonal pyramid tetrahedron
triangular prism
square pyramid
cube
pentagonal pyramid
pentagonal prism
tetrahedron
Octahedron
square pyramid
square antiprism
pentagonal pyramid
pentagonal antiprism

Elongated cupolae and rotundae

Elongated cupola Elongated rotunda Gyroelongated cupola Gyroelongated rotunda
Coplanar J18 J19 J20 J21 Concave J22 J23 J24 J25
Elongated fastigium Elongated triangular cupola Elongated square cupola Elongated pentagonal cupola Elongated pentagonal rotunda Gyroelongated fastigium Gyroelongated triangular cupola Gyroelongated square cupola Gyroelongated pentagonal cupola Gyroelongated pentagonal rotunda

Augmented from polyhedra
Square prism
Triangular prism
Hexagonal prism
Triangular cupola
Octagonal prism
Square cupola
Decagonal prism
Pentagonal cupola
Decagonal prism
Pentagonal rotunda
square antiprism
Triangular prism
Hexagonal antiprism
Triangular cupola
Octagonal antiprism
Square cupola
Decagonal antiprism
Pentagonal cupola
Decagonal antiprism
Pentagonal rotunda

Bicupolae

The triangular gyrobicupola is an Archimedean solid (in this case the cuboctahedron), so it is not a Johnson solid.

Orthobicupola Gyrobicupola
Coplanar J27 J28 J30 J26 Semiregular J29 J31
Bifastigium Triangular orthobicupola Square orthobicupola Pentagonal orthobicupola Gyrobifastigium Triangular gyrobicupola
(cuboctahedron)
Square gyrobicupola Pentagonal gyrobicupola

Augmented from polyhedron
Triangular prism Triangular cupola Square cupola Pentagonal cupola Triangular prism Triangular cupola Square cupola Pentagonal cupola

Cupola-rotundae and birotunda

The pentagonal gyrobirotunda is an Archimedean solid (in this case the icosidodecahedron), so it is not a Johnson solid.

Cupola-rotunda Birotunda
J32 J33 J34 Semiregular
Pentagonal orthocupolarotunda Pentagonal gyrocupolarotunda Pentagonal orthobirotunda Pentagonal gyrobirotunda
(icosidodecahedron)

Augumented from polyhedra
Pentagonal cupola
Pentagonal rotunda
Pentagonal rotunda

Elongated bicupolae

The elongated square orthobicupola is an Archimedean solid (in this case the rhombicuboctahedron), so it is not a Johnson solid.

Elongated orthobicupola Elongated gyrobicupola
Coplanar J35 Semiregular J38 Coplanar J36 J37 J39
Elongated bifastigium Elongated triangular orthobicupola Elongated square orthobicupola
(rhombicuboctahedron)
Elongated pentagonal orthobicupola Elongated gyrobifastigium Elongated triangular gyrobicupola Elongated square gyrobicupola Elongated pentagonal gyrobicupola

Augmented from polyhedra
Square prism
Triangular prism
Hexagonal prism
Triangular cupola
Octagonal prism
Square cupola
Decagonal prism
Pentagonal cupola
Square prism
Triangular prism
Hexagonal prism
Triangular cupola
Octagonal prism
Square cupola
Decagonal prism
Pentagonal cupola

Elongated cupola-rotundae and birotundae

Elongated cupolarotunda Elongated birotunda
J40 J41 J42 J43
Elongated pentagonal orthocupolarotunda Elongated pentagonal gyrocupolarotunda Elongated pentagonal orthobirotunda Elongated pentagonal gyrobirotunda

Augmented from polyhedra
Decagonal prism
Pentagonal cupola
Pentagonal rotunda
Decagonal prism
Pentagonal rotunda

Gyroelongated bicupolae, cupola-rotunda, and birotunda

These Johnson solids have 2 chiral forms.

Gyroelongated bicupola Gyroelongated cupolarotunda Gyroelongated birotunda
Concave J44 J45 J46 J47 J48
Gyroelongated bifastigium Gyroelongated triangular bicupola Gyroelongated square bicupola Gyroelongated pentagonal bicupola Gyroelongated pentagonal cupolarotunda Gyroelongated pentagonal birotunda

Augmented from polyhedra
Triangular prism
Square antiprism
Triangular cupola
Hexagonal antiprism
Square cupola
Octagonal antiprism
Pentagonal cupola
Decagonal antiprism
Pentagonal cupola
Pentagonal rotunda
Decagonal antiprism
Pentagonal rotunda
Decagonal antiprism

Augmented prisms

Johnson solids 49 to 57 are built by augmenting the sides of prisms with square pyramids.

Augmented triangular prisms Augmented pentagonal prisms Augmented hexagonal prisms
J49 J50 J51 J52 J53 J54 J55 J56 J57
Augmented triangular prism Biaugmented triangular prism Triaugmented triangular prism Augmented pentagonal prism Biaugmented pentagonal prism Augmented hexagonal prism Parabiaugmented hexagonal prism Metabiaugmented hexagonal prism Triaugmented hexagonal prism

Augumented from polyhedra
Triangular prism
Square pyramid
Pentagonal prism
Square pyramid
Hexagonal prism
Square pyramid

Modified Platonic and Archimedean solids

Johnson solids 58 to 83 are built by augmenting, diminishing or gyrating Platonic or Archimedean solids.

Augmented dodecahedra

J58 J59 J60 J61
Augmented dodecahedron Parabiaugmented dodecahedron Metabiaugmented dodecahedron Triaugmented dodecahedron

Augumented from polyhedra
Dodecahedron and pentagonal pyramid

Diminished icosahedra

Diminished icosahedra Augmented tridiminished icosahedron
J11
(Repeated)
Uniform J62 J63 J64
Diminished icosahedron
(Gyroelongated pentagonal pyramid)
Parabidiminished icosahedron
(Pentagonal antiprism)
Metabidiminished icosahedron Tridiminished icosahedron Augmented tridiminished icosahedron

Augmented Archimedean solids

Augmented truncated tetrahedron Augmented truncated cubes Augmented truncated dodecahedra
J65 J66 J67 J68 J69 J70 J71
Augmented truncated tetrahedron Augmented truncated cube Biaugmented truncated cube Augmented truncated dodecahedron Parabiaugmented truncated dodecahedron Metabiaugmented truncated dodecahedron Triaugmented truncated dodecahedron

Augumented from polyhedra
truncated tetrahedron
triangular cupola
truncated cube
square cupola
truncated dodecahedron
pentagonal cupola

Gyrate and diminished rhombicosidodecahedra

J72 J73 J74 J75
Gyrate rhombicosidodecahedron Parabigyrate rhombicosidodecahedron Metabigyrate rhombicosidodecahedron Trigyrate rhombicosidodecahedron

J76 J77 J78 J79
Diminished rhombicosidodecahedron Paragyrate diminished rhombicosidodecahedron Metagyrate diminished rhombicosidodecahedron Bigyrate diminished rhombicosidodecahedron

J80 J81 J82 J83
Parabidiminished rhombicosidodecahedron Metabidiminished rhombicosidodecahedron Gyrate bidiminished rhombicosidodecahedron Tridiminished rhombicosidodecahedron

Snub antiprisms

The snub antiprisms can be constructed as an alternation of a truncated antiprism. The gyrobianticupolae are another construction for the snub antiprisms. Only snub antiprisms with at most 4 sides can be constructed from regular polygons. The snub triangular antiprism is the regular icosahedron, so it is not a Johnson solid.

J84 Regular J85
Snub disphenoid
ss{2,4}
Icosahedron
ss{2,6}
Snub square antiprism
ss{2,8}
Digonal gyrobianticupola Triangular gyrobianticupola Square gyrobianticupola

Others

J86 J87 J88
Sphenocorona Augmented sphenocorona Sphenomegacorona

J89 J90 J91 J92
Hebesphenomegacorona Disphenocingulum Bilunabirotunda Triangular hebesphenorotunda

Classification by types of faces

Triangle-faced Johnson solids

Five Johnson solids are deltahedra, with all equilateral triangle faces:

 J12 Triangular bipyramid   J13 Pentagonal bipyramid   J17 Gyroelongated square bipyramid J51 Triaugmented triangular prism   J84 Snub disphenoid

Triangle and square-faced Johnson solids

Twenty four Johnson solids have only triangle or square faces:

 J1 Square pyramid   J7 Elongated triangular pyramid   J8 Elongated square pyramid   J10 Gyroelongated square pyramid   J14 Elongated triangular bipyramid   J15 Elongated square bipyramid   J16 Elongated pentagonal bipyramid   J26 Gyrobifastigium J27 Triangular orthobicupola   J28 Square orthobicupola   J29 Square gyrobicupola   J35 Elongated triangular orthobicupola   J36 Elongated triangular gyrobicupola   J37 Elongated square gyrobicupola   J44 Gyroelongated triangular bicupola   J45 Gyroelongated square bicupola J49 Augmented triangular prism   J50 Biaugmented triangular prism   J85 Snub square antiprism   J86 Sphenocorona   J87 Augmented sphenocorona   J88 Sphenomegacorona   J89 Hebesphenomegacorona   J90 Disphenocingulum

Triangle and pentagonal-faced Johnson solids

Eleven Johnson solids have only triangle and pentagonal faces:

 J2 Pentagonal pyramid   J11 Gyroelongated pentagonal pyramid   J34 Pentagonal orthobirotunda   J48 Gyroelongated pentagonal birotunda   J58 Augmented dodecahedron   J59 Parabiaugmented dodecahedron J60 Metabiaugmented dodecahedron   J61 Triaugmented dodecahedron   J62 Metabidiminished icosahedron   J63 Tridiminished icosahedron   J64 Augmented tridiminished icosahedron

Triangle, square, and hexagonal-faced Johnson solids

Eight Johnson solids have only triangle, square and hexagonal faces:

 J3 Triangular cupola   J18 Elongated triangular cupola   J22 Gyroelongated triangular cupola   J54 Augmented hexagonal prism J55 Parabiaugmented hexagonal prism   J56 Metabiaugmented hexagonal prism   J57 Triaugmented hexagonal prism   J65 Augmented truncated tetrahedron

Triangle, square, and octagonal-faced Johnson solids

Five Johnson solids have only triangle, square and octagonal faces:

 J4 Square cupola   J19 Elongated square cupola   J23 Gyroelongated square cupola J66 Augmented truncated cube   J67 Biaugmented truncated cube

Circumscribable Johnson solids

25 of the Johnson solids have vertices that exist on the surface of a sphere: 1–6,11,19,27,34,37,62,63,72–83. All of them can be seen to be related to a regular or uniform polyhedron by gyration, diminishment, or dissection.[3]

Octahedron Cuboctahedron Rhombicuboctahedron
J1

J3

J27

J4

J19

J37

Icosahedron Icosidodecahedron
J2

J63

J62

J11

J6

J34

 J5 J76 J80 J81 J83
 J72 J73 J74 J75 J77 J78 J79 J82

Dual Polyhedrons

As of now, the website https://levskaya.github.io/polyhedronisme/ supports Conway operations applied to Johnson solids. For example, see https://levskaya.github.io/polyhedronisme/?recipe=C1000dJ73&palette=%2300ffff%20%23ff7f7f for the dual polyhedron of J73.