Ryan Crystals 8489 were a composite explosive used for medium volume heat generation in emergency situations. In low pressure atmospheres, this explosive was preferred to conventional sarium krellide because of its superior infrared shock wave dispersion characteristics. In 2367, this explosive was stored on aboard the Federation starship USS Enterprise-D.
In that year, Ryan Crystals 8489 was on a list of explosives that Lieutenant Commander Data and Counselor Deanna Troi searched through in an attempt to find one that could produce enough energy to release the USS Enterprise-D and an alien ship from the Tyken's Rift. (TNG: "Night Terrors")