Albert Barnes Commentary Job 28:16

"It cannot be valued with the gold of Ophir, With the precious onyx, or the sapphire." — Job 28:16 (ASV)

The gold of Ophir - Uniformly spoken of as the most precious gold; see the notes at (Job 22:24).

With the precious onyx - The onyx is a semi-pellucid gem, with variously colored veins or zones. It is a variety of the chalcedony. The Arabic word denotes that which was of two colors, where the white predominated. The Greeks gave the name “onyx” ὄνυξ onux to the gem from its resemblance to the color of the thumbnail; see Passow.

Or the sapphire - See the notes at (Job 28:6).