>>14032028There are three types of patches when chaining. Regular shaking grass, sparking grass (this type can contain pokeradar exclusive pokemon), and shiny patches. The shiny patches will glow on and off with some sparkles in them. When you see one for the first time it really stands out, but like all other patches it only shakes for about a second so you need to keep your eyes out for it.
pic related, best one I could find from google.