Tandgor gems.
Tandgor gems originated from the planet Tandgor, situated in the Outer Rim, and were known for their high cost and vibrant red glow. On one occasion, Han Solo and Chewbacca engaged in smuggling these precious stones.
These gemstones are featured solely within a story from Star Wars Tales, a series with uncertain canonicity. Nevertheless, the planet Tandgor's existence is indeed validated within The Essential Atlas.