Basically, cream gleam is Elopor - in entire mountains made mostly of it, and some little ‘ancient temple’ prefabs have 1 cream gleam under them. iirc Epsilo also has mini-mountains of cream gleam underwater in the oceans, though they are hard to get without drowning
Red gleam, as @the-moebius has said, is now extremely rare.
Blue gleam is under graves in Munteem. Yellow gleam is under graves in Nasharil.
As for the metals, I have personally had the most luck with gold, silver, and titanium just above the lava layer.
Diamond is quite rare as it is technically a gem. Check the gem location guide for more on those.
As for marking resource locations, from what I understand the more an area is traversed and mined, the less chance that regen will spawn any high value resources there next time. Somone please correct me if I am wrong about that.
