sparkle of jewelry, crystal
瑛 centers on the bright, clear sparkle of precious stones and crystals, like light catching a jewel.
瑛 combines 王 (jewel) with 英, which likely contributes both sound and the idea of brilliance or luster, together suggesting a sparkling gem.
The jewel radical 王 beside 英 (which suggests brilliance) makes a sparkling crystal: a jewel that shines brightly.
For エイ, picture a sparkling crystal shaped like the letter A: A -> エイ, and its facets catch the light.
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crystal; transparent gem