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This is the case for many materials. The raw material itself is not rare, the bottleneck is the refining/processing capability and thus the refined material is scarce.

- The shortage of lumber in US a few years was due to lack of saw mills, not trees

- Shortage of semi-conductor grade Neon due to lack of plants that can refine the gas to the required purity

- Shortages of oil derived products due to constraints on refining

- "Rare earth" shortages as few countries refine. China is one of the few countries willing to tolerate the pollution generated from the refining processes.