If the enemy Skarner captures one of his Crystal Spires, it immediately turns red on the minimap, and you can even put your camera over it to see how recently he captured it (it has a cooldown animation).
This means that Skarner can't counter-jungle effectively. Either he captures and gives away his position, or takes forever to clear and risks running into the enemy jungler.
It also means he can't sneak Dragon, Herald, or quickly take Scuttle, without letting the whole map know.
The crystals shouldn't give away their status until your team has vision on them.
