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Foundation 6 of 12
Revelation 21:20

Sardius

σάρδιον

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

Mineralogy
Greek name
sardion (σάρδιον)
Modern identification
Carnelian / Sard
Chemical formula
SiO₂
Crystal system
Trigonal
Optical class
Uniaxial (+)
Birefringence (Δn)
0.004–0.009
Refractive indices
1.530–1.539
Color / appearance
Reddish-orange to brown

Iron oxide coloring; used in ancient Near East seals.

The light between

Sardius is anisotropic: enter it with a single ray of light and it leaves as two, split apart by the crystal's inner order. This is birefringence, the same property shared by every one of the twelve foundation stones, and by none of the cubic stones left out of the list.

In the high-priestly breastplate of Exodus 28, this position held Jasper in the Septuagint reckoning.

Hold the light in your hand

The Revelation Stones collection brings each foundation stone into the room with you, and the Light Between research explains what you are looking at.