This is the 6379th most frequent Polish word.
bursztynową
"Amber" (adjective form, feminine singular).
Here, 'bursztynową' is used as an adjective describing the color of the shell, metaphorically comparing its appearance to amber.
Podczas spaceru nad morzem znalazłem bursztynową muszlę.
During a walk by the sea, I found an amber-colored shell.
In this sentence, 'bursztynową' is an adjective qualifying the noun 'tea,' referring perhaps to its amber-like abundant color.
Zamówiłem bursztynową herbatę w kawiarni.
I ordered amber tea at the café.
Here, 'bursztynową' describes the material of the chessboard, translating to 'made from amber.'