What is the origin of 'sleep tight'?
Read moreOne of the mysteries of the English language finally explained.
An orthorhombic fluoride of sodium and magnesium, NaMgF₃, which occurs as colourless to pink crystals, isostructural with perovskite. Also ("potassium neighborite"), a similar mineral in which potassium replaces sodium.
1960s. From the name of Frank Neighbor, U.S. geologist + -ite.