Does this item retain the 1 minute casting time for Conjure Elemental or is the summoning instantaneous in this case?

This answer's a little late, but it says you "use an action to... summon an air elemental" *as if* you had cast conjure elemental. So no, it does not take a minute to cast the spell. You're using an action to get the effects of what would take 1 minute to cast. But it does still require concentration to maintain.

Oh, no worries, it wasn't a time sensitive thing, I've just been curious about this item I've had all campaign. Thanks for the clarification! Better late than never :)

Also note how the wording says "as if you HAD cast". In other words, the effect happens after the "casting" has concluded, so the casting time doesn't really matter.

(Also also, keep in mind that while I say "casting", you never actually cast anything. That's why this also doesn't take up a spell slot.)

Stupid, should def be attunement

Then make it so in your game

Does the summoning require concentration like the spell?  Or is the focus for the cast held by the object?  

Requires concentration