As a solver and collector of twisty puzzles who also enjoys horror fiction, I do occasionally seek out puzzles that look like they should summon demons or open portals to Hell. Bonus points if they shape shift. The following is a strange journey into weird fiction, geometry, the history of literature, and mineralogy.

I have wondered for a long time exactly what shape H.P. Lovecraft was imagining for the Shining Trapezohedron in his short story The Haunter of the Dark. In the story, the Shining Trapezohedron is an unusual stone of alien origin that summons a malign supernatural entity, leading to the horrific demise of the protagonist. Descriptions in the story include “irregularly spherical object some four inches through” and “a nearly black, red-striated polyhedron with many irregular flat surfaces”.

At some point, I would very much like to acquire a twisty puzzle in the shape of that trapezohedron, especially if it happens to shape shift.

Much to my surprise, a member of the H.P. Lovecraft Historical Society did some research, and reported on a possible physical artifact that was the Lovecraft’s inspiration for the Shining Trapezohedron. The report summarizes some interesting facts, including the distinction between a geometrical trapezohedron and a mineralogical trapezohedron. It also notes that many artists have depicted the Shining Trapezohedron as a geometrical trapezohedron of some kind. The likely mineral specimen that was the inspiration for the story was a large crystal of garnet, tracked down to the Paterson Museum in New Jersey.

As I read the report, I looked at the photos of the stone, and realized that the angles looked wrong. Fortunately, I have a puzzle in the shape of a rhombic dodecahedron, which is one of the other crystal habits that garnet can crystalize into. I aligned the puzzle to the same orientation as the photos in the article, and saw that the same facets were visible as in the photos. If the crystal in the museum had been a trapezohedron, more facets would have been visible at once than were shown in the photos.

I concluded that the author of the article did find a remarkably large garnet crystal that might have inspired Lovecraft, but it was not in the shape of a (mineralogical) trapezohedron. Instead, the crystal was in the more common rhombic dodecahedral crystal habit of garnet.

While researching other large garnet crystals, I came across the Subway Garnet of New York City, which is another large garnet crystal that is of predominantly trapezohedral crystal habit. Its shape actually a hybrid of the three main crystal habits of garnet, but the trapezohedron seems to dominate. The Subway Garnet was found in 1885, and it’s plausible that it was on display in NYC before Lovecraft wrote The Haunter of the Dark. He might have actually been able to see it while it was on public display.

I suspect that Lovecraft made a synthesis of these two physical specimens to produce the fictional Shining Trapezohedron in his short story. The result is one of the most memorable gemstones mentioned in weird fiction.

I did find a puzzle in the shape of a deltoidal icositetrahedron, which is the geometrical name of the mineralogical trapezohedron. It is a shape shifting puzzle, and has a high complexity that gives it an otherwordly appearance. Unfortunately, it is not mass produced. Even a kit of the 3D-printed pieces is rather expensive, and it is even more expensive to have the designer assemble and sticker it. I do hope to acquire or build one someday.