Tai

"Let me have a closer look at that," Tai says of the amethyst.
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Not sure which Knowledge is necessary, but their all about the same: (1d20+12)[16]

If it's not Arcane, the result is +10, with the use of Cunning Knowledge.
If it is Arcane, the result is +5, thanks to his Tome of Ancient Lore, which he peruses each morning.
If it happens to be Nature or Psionics, it is +2 more, thanks to some synergy bonuses.