If you’re on abb I would recommend going into the Red zone and mining some. But if on genesis just go to the ocean biome and go to one of the underwater tek cubes and one of them has all 3 crystal types in it hope this helped.

Abb radiation zone on Valguero I think gives the most per crystal. You get red and blue gems

The bubbles in crystal isles has alot of them

You need these for drake saddles

Just use a doedicurus, it gets so much red gems

If you're on Extinction lategame, use tek gloves to farm them in the Sulfer biome.

Abeeration coords 40 68 in blue zone there is a cluster