BDB2182
יַהֲלֹם noun [masculine] a precious stone, jasper? (so ᵐ5 ᵑ9 ), or onyx? (compare Di Exod 28:18) (apparently from √ הלם; owing to its hardness, as able to smite, hammer?) — mentioned in lists of precious stones Exod 28:18; Exod 39:11; Ezek 28:13.