@Wyntyr
https://docs.google.com/spreadsheets/d/1H8QWIOz5AZX-461Vg5KTQ2l192Ne0GwsH9UiVSrAKx0/edit?usp=sharing
So first off, my design has 100 possible purity "tiers" for any resource. In my example the quality is in 1% increments until you reach 98% where it becomes much finer. The actual displayed numbers are technically irrelevant, from the game mechanics standpoint.
The bottom purity tiers are what you find in the ground, Eg 40% Iron, 60% "dirt", or 25% iron, 25% Sulfur Dioxide, 50% "dirt". The cutoff I placed at 69% which is the highest you will ever find in the ground. Like FF a region will have a density map, so the purity for any one element will vary all the way from min to maximum within that range. The key is that ALL of it is useful, because you can refine any purity into a higher purity through processing. What is critical is that there is no one purity for an entire map, so players won't be limited in finding "rare" high quality tiers. There should always be a wide range on any one region, provided a player is willing to spend the time hunting them down.
And that time will definitely be worth while. Processing takes time, and you also loose a chunk of your total value for each purity tier you improve. In my spreadsheet I set it at 5% loss per tier. This represents unrecoverable material, known in the industry as tailings. If you only want to upgrade the purity of a chunk of resource by a few tiers, it won't be too bad, but that 5% is per level so it can quickly add up. As such, starting with a high purity resource will save you a lot of thumping time.
In the link above, to go from tier 100 to tier 1 requires you to input over 12,000 units in order to get out 100. Obviously the numbers themselves can be manipulated, but the point stands that being a vacuum cleaner won't automatically get you way ahead of anyone else (but at the same time it still is useful).
Above the purity tiers found in the ground are purities sufficient to be turned in for buildings or world tier progression. Less processing is required on the players part, the higher the purity however the better whatever rewards system Grummz puts in place will get you. I could see some RNG in the reward system where the higher the quality (and amount) the better your odds are or something. But that is another topic.
Only the top tier purity levels can be used for crafting. 100% purity may not always be the end goal however. 100% pure iron for example is great, but adding a small amount of impurity is how we get steel. So too we can use the purity of our resources to tie to multiple end effects with varying curves, not all of which top out at the 100% mark. Eg. Resource X is needed for crafting jump-jets, at 90% purity it provides 110 fuel cap, and 12.8 m/s lift. at 100% purity it would provide only 80 fuel cap but 15.2 m/s lift. The former would be better for hovering, the later for quick bursts of speed.
The goal here is to make sure that nothing is wasted, and everyone can be on an even footing. You will never have resources that simply sit in your inventory unused, because they can either be "upgraded" to fit your needs, or donated.