The answer is: An onyx

Exo 28:9 - to be part of the priestly ephod

In the ancient world, onyx stones were quite special, not just for their beauty, but also for their symbolism. The names of the twelve tribes of Israel engraved on the onyx stones represent more than just markers of identity; they embodied the unity and diversity of a community journeying together. Each name, each tribe carries its own stories and histories, echoing the rich tapestry of the people.

The fact that these names were set upon the priestly ephod reminds us of the importance of the priest's role in mediating between the people and the Divine. The High Priest wore this distinctive garment not just as a piece of clothing but as a visible expression of responsibility. It served as a reminder that every tribe had a place in the promises and covenant introduced by God.

Additionally, do you know that onyx features in other significant biblical contexts? It's mentioned in the Garden of Eden as part of the land’s wealth (Genesis 2:12). This ties beautifully back to the idea of God providing not only physical sustenance but also a rich spiritual heritage for both the individual tribes and Israel as a whole.

So, the onyx doesn’t merely serve an aesthetic function. It reinforces the relationship between God and Israel, highlighting His attentiveness to each tribe’s presence and calling. Every bit of engraved stone boldly declares, “You are my people!” It’s all whimsically intertwined—stones, names, tribes—a colorful quilt of divine intention!