@peachfront @futurebird Yes, the inter-webs tell me that although other harvester ants have dug garnet in Australia and Africa, the main (trusted) source is the Navajo Nation, in the Four Corners region of northeastern Arizona where they carefully document the available (chromium rich) pyrope garnets. Mantle-derived, they occur in shallow, weathered deposits reachable by ants, which conditions don't often occur elsewhere. I have seen them listed briefly for sale on line, 1-5 mm roughs in lots.

@futurebird You can buy them loose, but not set; they're usually small, under a quarter carat, and never faceted at that size. There are indigenous sites I think in Arizona where you can go pick them up yourself for a fee.
I've heard gem sellers call them "anthill garnets" and since garnets are all natural, never treated or enhanced, you have just your ant friend to thank.
Garnets were known for invisibility in battle and for strengthening your blood (vigor) and sex drive.