Surmised, the Hammer Parts look identical to the Amy's Hammer, but come in a different size.
In the gameplay of Sonic Boom: Fire & Ice, there are a total of sixty Hammer Parts which are hidden in the adventure levels. Each level holds three Hammer Parts, each of which can be collected by opening an item capsule resembling a golden bubble with a Hammer Part inside it. These capsules break when touched and can be targeted with the Homing Attack.
When obtained, the Hammer Parts can be brought to Amy's House to be put on display in Amy's display case. For every tenth Hammer Part the player recovers, they will unlock a new skin for Amy's Hammer in gameplay which can be equipped in Amy's House.
List of hammers