We examine tracks in crystals of muscovite of high energy charged particles, and of mobile lattice excitations created by kinetic atomic scattering. The mobile lattice excitations are interpreted as a type of breather, here called a quodon. The typical energy of a quodon can be found from the decay of potassium K 40 atoms in the crystal and supports their interpretation as a type of breather. In turn, this establishes a unique signature for energetic quodons, the 'kinked-line' tracks, allowing discrimination against tracks formed by charged particles. The stability of quodons against crystal defects and thermal motion is considered. Measurements on energetic quodon tracks, with flight paths up to 530mm, show that they can propagate more than 10 9 unit cells with no evidence of energy loss. This suggests that quodons might persist indefinitely in certain crystals of high quality. Evidence is presented for a new type of mobile lattice excitation that is capable of creating energetic quodons, which also is stable against lattice defects. Possible practical applications of quodons are considered briefly. Although quodons can induce fusion in deuterium or tritium, present indications are that the rate is too low to be of practical use. Finally, a nonlinear lattice effect that might increase this rate is suggested.