Great enneagrammic antiprismatic prism

The great enneagrammic antiprismatic prism or gisteappip is a prismatic uniform polychoron that consists of 2 great enneagrammic antiprisms, 2 great enneagrammic prisms, and 18 triangular prisms. Each vertex joins 1 great enneagrammic antiprism, 1 great enneagrammic prism, and 3 triangular prisms. As the name suggests, it is a prism based on the great enneagrammic antiprism. Being a prism based on an orbiform polytope, it is also a segmentochoron.

Vertex coordinates
The vertex coordinates of a great enneagrammic antiprismatic prism with edge length 2sin(4π/9) are given by: where $$H=\sqrt{\frac{1+2\cos\frac{4\pi}9}{2+2\cos\frac{4\pi}9}}\sin\frac{4\pi}9.$$
 * $$\left(1,\,0,\,±H,\,±\sin\frac{4\pi}9\right),$$
 * $$\left(\cos\left(\frac{2\pi}{9}\right),\,±\sin\left(\frac{2\pi}{9}\right),\,±H,\,±\sin\frac{4\pi}9\right),$$
 * $$\left(\cos\left(\frac{4\pi}{9}\right),\,±\sin\left(\frac{4\pi}{9}\right),\,±H,\,±\sin\frac{4\pi}9\right),$$
 * $$\left(-\frac12,\,±\frac{\sqrt3}{2},\,±H,\,±\sin\frac{4\pi}9\right),$$
 * $$\left(\cos\left(\frac{8\pi}{9}\right),\,±\sin\left(\frac{8\pi}{9}\right),\,±H,\,±\sin\frac{4\pi}9\right),$$

Representations
A great enneagrammic antiprismatic prism has the following Coxeter diagrams:
 * x2s2s9/4s (full symmetry)
 * x2s2s18/4o
 * xx xo9/4ox&#x (great enneagrammic prism atop great enneagrammic prism)