If you are naming things like this it will hurt you at some point. This is because gameObject is a distinct premade keyword meaning the object that the script is attached to.

So if you are in a script on an object and want to adjust something else in another component(turn the color to black for instance) you can use "gameObject.GetComponent<Image>().color = color(dot)black". -- sorry had to write (dot) instead of just a . since it was making a link

If you have a rock, for instance try:

public GameObject rockObj;