Almost always reduplicated (熠熠) and almost always literary. The set phrase 熠熠生辉 (yìyì shēnghuī, 'shining radiantly') is the most common context — used for stars, jewels, eyes, and metaphorically for outstanding talents or achievements.
memory
Note the 火 (fire) radical in 熠 — the character is built around the idea of glowing light, just like 烁 (shuò) and 燿 (yào). Reduplication 熠熠 intensifies the shimmer into a continuous glittering effect.
