Colorless beryl, var. goshenite, which is permeated with very fine scheelite dust and thus fluoresces in shortwave UV. Xuebaoding Mine, Pingwu, Sichuan, China.
This spectrum compares the emission of a scheelite specimen to that of beryl var. goshenite. The fluorescence of the beryl crystal is clearly caused by ultrafine scheelite dust that was incorporated during growth. The smaller peaks on the red graph are caused by rare earth elements such as samarium, dysprosium, europium and, around 900 nm, neodymium. Very small traces of those show up in the scheelite that is included in the beryl... just barely visible but clearly there.
Source: Axel Emmermann, MKA http://fluo.mineralogie.be/index.html