Hop Rocks looked like small, bluish-purple crystals. They were added to the game in Season 4, and removed in Season 5. They could be found in any crater around the map, such as Dusty Divot and the small crater in the prison next to former Moisty Mire.
They are added once more in Season X. The third Rift Beacon destroyed the Rec Center (the one with the indoor Soccer Stadium) and made Glitch Consumables. These consumables can turn into any consumable in Fortnite’s history including Hop Rocks themselves. They are removed again at the start of Chapter 2: Season 1 due to the new map.
Hop Rocks worked like Chests, Ammo Crates, Loot Llama, and Supply Drop, but they didn't let out loot. When pressed, they will appear in the players' hands, then disappear. Affected players will then pulse with bluish-purple light, and when they jump, it will be much higher than usual and the light will be stronger. This lasted for about 30 seconds.
When using a launch pad with the effect of the Hop Rock, you could launch much higher than if you used a launch pad without it.