The gold of Ophir was the best sort of gold. See Poole on "1 Kings 9:28", See Poole on "Job 22:24". Onyx, or sardonyx. See Poole on "Exodus 28:20".
Related Commentaries of Job 28:16
Job 28:16
16 It cannot be valued with the gold of Ophir, with the precious onyx, or the sapphire.