except for the food resource, each tech will reveal one resource.
NOTE: the ai can research this tech as well and it will spawn when he doe sit so if you see one suddenly spawning for no reason, thats where it came from.
The mining tech can reveal a gold mine, or clay mine or ore mine, ventri if your lucky.
channeling will reveal a crystal mine, there used to be an adventure tech to reveal a crystal mine - not sure if it still does that so you might have the opportunity to spawn a second crystal mine.
When it comes to the resource revealing techs, strategically these are really good if you've explored the territory around you and the ai does not have something you want. They can help fill in the gaps to keep you competitive against the ai if they are ahead of you and you really need metal badly to put out those armoured units.
Whether it spawns a resource or reveals a resource that is already there is really irrelevant when it comes down to the final fact - suddenly it is there and you can see it. The dev's have stated that due to the nature of the way cities operate withing the game structure it is better to spawn the resource rather than suddenly reveal it otherwise you would have all sort of "?" items dotted all over the landscape which would be unknown resource icons. Sort of immersion breaking for me if all those icons were there.
The manner in which they have done it does not make the first player to learn harvesting suddenly make all these resources appear over the entire map structure. "I was gonna build my house there, suddenly the ground open up and bees poured out of the ground - I HATE THOSE CHANNELLERS MESSING WITH MY GREEN LAWN".
The intention of the tech is you send out your scouts who work for you in the background and they search the land near your capital until they find the nearest resource and then point it out to you. It does not mean they found all of the food resources in world etc, or suddenly that we understand that bees make food for us to eat