Gregoryite is an anhydrous carbonate mineral that is rich in potassium and sodium[5] with the chemical formula (Na2,K2,Ca)CO3.

[2][6][7] It is one of the two main ingredients of natrocarbonatite, found naturally in the lava of Ol Doinyo Lengai volcano of Arusha Region, Tanzania, and the other being nyerereite.

[8] Because of its anhydrous nature, gregoryite reacts quickly with the environment, causing the dark lava to be converted to white substance within hours.

[5] Gregoryite was first described in 1980 and named after the British geologist and author John Walter Gregory (1864–1932), who studied the East African Rift Valley.

[2][3] It occurs associated with nyerereite, alabandite, halite, sylvite, fluorite and calcite.