«وَقَمَرُهَا كَتَعْوِيذٍ مِنْ لُجَيْنٍ»
Its moon resembled a small amulet made of silver.
The moon is compared with a small silver amulet. The preposition ka- makes resemblance explicit. The image can evoke gleam, shape and apparent smallness within a night scene.
Nothing says the moon is made of silver. Treating similarity as material identity would turn a poetic comparison into a false scientific statement. The figure invites perception, not literal classification.
“The moon appeared like silver” is comparison; “the moon consists of silver” is not asserted.