This pendant has the circle constant tau on one side, and the Taoist yin-yang on the other, for a reversible look. With a 1 cm radius, the pendant has a circumference of exactly tau (6.28) cm.

This pendant has the circle constant tau on one side, and the Taoist yin-yang on the other, for a reversible look. With a 1 inch radius, the pendant has a circumference of exactly tau (6.28) inches.

With a 1 cm radius, the pendant has a circumference of exactly tau (6.28) cm.

A tesseract is a four-dimensional hypercube — a cube’s analog in four dimensions. In Madeleine L’Engle’s “A Wrinkle in Time,” the protagonist Meg “wrinkles time” through a tesseract, which acts as a portal or worm-hole leading to another part of space-time.
This pendant is 1.3 in (3.3 cm) from top to bottom, including the loop.

Want to give the gift of diamond without breaking the bank, or the backs of diamond mining slaves? You’re in luck. Here is a pendant featuring the molecular structure of diamond! Just loop a chain through the structure for a whimsical look that is sure to spark conversation. The spheres represent carbon atoms.

Prussian Blue is a beautiful color, and it’s also beautiful on the molecular scale. One of the first synthesized pigments, Prussian blue has been used in painting for hundreds of years, and scientists continue to find new uses for this non-toxic compound. The larger two ion sizes on the corners of the lattice are Iron(III) and Iron(II), while the smaller pairs are Carbon and Nitrogen.