Is a Gem of Seeing always active?

[Super_Troll]

I have a player who had a Gem of Seeing put into something akin to a pair of goggles.
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Gem of Seeing

This finely cut and polished stone is indistinguishable from an ordinary jewel in appearance. When gazed through, the gem of seeing enables the user to see as though she were affected by a true seeing spell.

Caster Level: 10th; Prerequisites: Craft Wondrous Item, true seeing; Market Price: 75,000 gp; Weight: -.

 

[kreynolds]

By default, rings are generally the only magic items that function constantly (unless stated otherwise). So, the gem would be activated as a standard action and would function for 10 minutes before it would need to be activated again.

 

[AEtherfyre]

Eh. Given that it says "when gazed through" and doesn't seem to directly imitate the spell, I'd say it takes up a hand-slot whenever you'd use it, but I'm not sure what I'd do with combat - is it really possible to hold something right in front of your eye mid fight?

In any case, that's all my opinion, and not really supported by the rules.