The twelve stones are to correspond to the names of the sons of Israel, each engraved like a seal with the name of one of the twelve tribes.

Revelation 7:4
And I heard the number of those who were sealed, 144,000 from all the tribes of Israel:

Revelation 21:12
The city had a great and high wall with twelve gates inscribed with the names of the twelve tribes of Israel, and twelve angels at the gates.

Exodus 28:11
Engrave the names of the sons of Israel on the two stones the way a gem cutter engraves a seal. Then mount the stones in gold filigree settings.

Exodus 28:20
and in the fourth row a beryl, an onyx, and a jasper. Mount these stones in gold filigree settings.

Exodus 28:22
For the breastpiece, make braided chains like cords of pure gold.

And the stones shall be with the names of the children of Israel, twelve, according to their names, like the engravings of a signet; every one with his name shall they be according to the twelve tribes.