Twelve stones. Every one splits light.

An aggregate of countless tiny quartz crystals: every one of them splits light, even where the whole stone looks opaque.

Dichroic: it shows two different colors depending on the direction light travels through it.

Its fibrous quartz threads bend light into shifting, anomalous interference patterns.

The pivotal stone: where the breastplate had garnet (which cannot split light), Revelation has emerald, the swap that makes all twelve stones split light.

Banded layers of light- and dark-toned quartz, each band still splitting light at the crystallite level.

The seal-stone of the ancient world: iron-tinted quartz whose every grain refracts light in two.

Splits light so strongly that in a large stone you can see doubled edges with the naked eye.

Emerald's kin without the chromium: the same light-splitting lattice in aquamarine, gold, and rose.

Strongly pleochroic: its color shifts with the angle of the light passing through.

The rarest chalcedony: nickel lends it apple-green, while the quartz beneath still divides the light.

The strongest light-splitter of the twelve: look through it and the far edges appear doubled. Visible in antiquity, unexplained until 1690.

The last foundation is quartz that keeps time: piezoelectric, it sets the frequency in modern oscillators and clocks.