Data Crystals are crystals used by the Goa'uld and possibly Ancients to store information. One of these Crystals was used by the Goa'uld Thanos on the planet Langara. On this Crystal was the information about Naquadria. Her'ak tried to steal the Data Crystal that had information on Naquadria, but failed and Jonas Quinn and his nation was able to get information from it. (SG1: "Homecoming")