"The rays are sometimes very short, or altogether wanting, the body having the form of a pentagonal disk." — Encyclopedia Britannica, 1893

Astrogonium Phrygianum

"The rays are sometimes very short, or altogether wanting, the body having the form of a pentagonal…

Represents a combination of a pentagonal dodecahedron and cube, and are common in pyrites.

Combination of Pentagonal Dodecahedron and Cube

Represents a combination of a pentagonal dodecahedron and cube, and are common in pyrites.

"...resembles in general appearance the regular icosahedron of geometry, but only eight f the faces are equalateral trianges." -The Encyclopedia Britannica 1910

Combination of Pentagonal Dodecahedron and Octahedron

"...resembles in general appearance the regular icosahedron of geometry, but only eight f the faces…

Represents the combination of pentagonal dodecahedron, cube, and octahedron.

Combination of Pentagonal Dodecahedron, Cube and Octahedron

Represents the combination of pentagonal dodecahedron, cube, and octahedron.

Represents the combination of pentagonal dodcahedron, dyakis-dodecahedron and octahedron.

Combination of Pentagonal Dodecahedron, Dyakis-dodecahedron, and Octahedron

Represents the combination of pentagonal dodcahedron, dyakis-dodecahedron and octahedron.

Right circular cylinder inscribed in a pentagonal prism. Or, Pentagonal prism circumscribed about a cylinder.

Cylinder Inscribed in Pentagonal Prism

Right circular cylinder inscribed in a pentagonal prism. Or, Pentagonal prism circumscribed about a…

Illustration of a pentagonal prism inscribed in a cylinder.

Prism inscribed in Cylinder

Illustration of a pentagonal prism inscribed in a cylinder.

A flashcard featuring an illustration of a Pyramid with a Pentagonal Base

Flashcard of a Pyramid with a Pentagonal Base

A flashcard featuring an illustration of a Pyramid with a Pentagonal Base

"This is bounded by twelve pentagonal faces, but these are not regular pentagons, and the angles over the three sets of different edges are different. The regular dodecahedron of geometry, contained by twelve regular pentagons, is not a possible form in crystals." -The Encyclopedia Britannica 1910

Pentagonal Dodecahedron

"This is bounded by twelve pentagonal faces, but these are not regular pentagons, and the angles over…

"This is the only simple form in this class which differs geometricalled from those of the holosymmetric class...These are each bounded by twenty-four irregular pentagons, and althrough similar to each other they are respectively right- and left-handed..." -The Encyclopedia Britannica 1910

Pentagonal Icositetrahedron

"This is the only simple form in this class which differs geometricalled from those of the holosymmetric…

Illustration of a right pentagonal prism with regular pentagons for bases and rectangular faces. The height of the prism is greater than the length of a side of the pentagon. The hidden edges are shown.

Pentagonal Prism

Illustration of a right pentagonal prism with regular pentagons for bases and rectangular faces. The…

Illustration of a right pentagonal prism with regular pentagons for bases and rectangular faces. The height of the prism is slightly greater than the length of a side of the pentagon. The hidden edges are shown.

Pentagonal Prism

Illustration of a right pentagonal prism with regular pentagons for bases and rectangular faces. The…

Illustration of a right pentagonal prism with regular pentagons for bases and rectangular faces. The height of the prism is slightly greater than the length of a side of the pentagon.

Pentagonal Prism

Illustration of a right pentagonal prism with regular pentagons for bases and rectangular faces. The…

Illustration of a right pentagonal prism with regular pentagons for bases and rectangular faces. The height of the prism is greater than the length of a side of the pentagon.

Pentagonal Prism

Illustration of a right pentagonal prism with regular pentagons for bases and rectangular faces. The…

The frustum of a pentagonal pyramid is the portion of a pyramid included between the base and a section parallel to the base.

Frustum of Pentagonal Pyramid

The frustum of a pentagonal pyramid is the portion of a pyramid included between the base and a section…

"This is bounded by twelve irregular pentagons, and is a tetartohedral or quarter-faced for of the hexakis-octahedron." -The Encyclopedia Britannica 1910

Tetrahedral Pentagonal Dodecahedron

"This is bounded by twelve irregular pentagons, and is a tetartohedral or quarter-faced for of the hexakis-octahedron."…