Lustrous means shining with a soft gleam. Lustrous hair, a lustrous pearl, lustrous silk.
The shine is soft and deep rather than hard and bright, which is why the word suits hair, pearls and silk and not metal or glass. In mineralogy the same quality is called lustre and is used to identify stones. Note lustre, the noun, from the Latin for light.
1adjectivelustrousShining with a soft gleam.
“She brushed her long, lustrous hair until it shone.”
lustrous is a quality of shine.
Proto-Indo-European
*lewk-
Middle French
lustre
English
lustre
English, today
lustrous
From lustre + -ous. lustre comes from Middle French lustre. See luster (etymology 1).
Etymology from Wiktionary, CC BY-SA