Grindelwald is an inhabited planet that possesses rich deposits of trillium.
In 2366, the USS Enterprise visited Grindelwald, where several of its crew took shore leave. William Riker and Geordi La Forge discovered several Ferengi, who were secretly and illegally mining the trillium. Riker and LaForge, along with Worf, would later stop the Ferengi. (TNG comics: "Holiday on Ice", "Prisoners of the Ferengi")