This is the 10224th most frequent Russian word.
блестящими
"Shiny" or "brilliant."
In this sentence, "блестящими" describes the sparks of joy, emphasizing their brilliance and shine.
Её глаза сияли блестящими искрами радости.
Her eyes sparkled with brilliant sparks of joy.
Here, "блестящими" refers to the glittering or shining quality of the jewelry items.
На празднике все восхищались её блестящими украшениями.
At the celebration, everyone admired her glittering jewelry.
In this case, "блестящими" metaphorically describes the answers as being exceptionally good or smart.