See Polling rock sample contents help .
Detecting the additional transitions mentioned in Greg’s reply are the primary case in favour of rolling this feature into a PR on GT core.
Indicator flowers and found ore blocks work client-side.
As for the rocks…
The server alone has the worldgen TileEntity data of which rock / raw ore is stored inside the rock; when it is clicked, the server puts that directly into the player’s inventory, and the server then authoritatively updates the client’s inventory to contain that rock. A pure client-side mod has no access whatsoever to the mineral type that will be produced by the rock, which gives the false negative of Everything being basic rock layer material, it cannot detect ore rocks.
… a server portion of the mod is required.
Alternately, one could try to detect the inventory changed when the rock was added, as was suggested on my modpack Discord – best of luck discarding every time you take rocks out of a chest, de-craft a block of raw ore, pick up a rock that was dropped into the world, or otherwise gain a rock (in addition to the inaccuracy of having entity float position & look direction instead of tile coordinates).