Board Thread:General Discussion/@comment-5891711-20150624083039

So at first I assumed that Garnet, Amethyst, and Pearl were just a random selection of gemstones, but then I was playing Sonic Adventure (which came out at least a decade ago) and saw something that caught my attention.

There are four courses for Chao racing in that game: Pearl, Amethyst, Sapphire, and Ruby (which are obviously Garnet when not fused).

Is there a certain significance to those four being the selection? I can't seem to find connections between the gemstones themselves. 