Lithium molybdate has been prepared by grinding LiOH·H₂O with MoO₃ in air at room temperature. X-Ray powder diffraction data show that the formation of highly crystalline Li₂MoO₄ is largely complete after 10 min. The phenacite structure of this material is the same as that derived from an X-ray diffraction study of a single crystal obtained from aqueous solution [R; a = 14.3178(14) Å, c = 9.5757(9) Å]. Anhydrous lithium hydroxide fails to give the same reaction indicating that the water of crystallisation of LiOH·H₂O is a vital component in this rapid synthesis. Differential scanning calorimetry measurements show that this reaction can proceed spontaneously between the two stable solid reagents at sub-ambient temperatures and is driven by the liberation of water from the crystalline lattice. Lithium molybdate prepared in this manner has significantly smaller and more regularly shaped particles than samples prepared by other synthetic methods.