Micro‐Raman study of cesanite (Ca₂Na₃ (OH)(SO₄)₃) in chloride segregations from Udachnaya‐East kimberlites

Cesanite (Ca₂Na₃(OH)(SO₄)₃₎, a rare mineral, has been found in a few places restricted to a geothermal field and caves. We report the new occurrence of cesanite in quite different geological site—within sulfate‐rich melt inclusions in chloride segregations from kimberlites of Udachnaya‐East pipe (Siberia). Two halite generations: сesanite free and сesanite‐bearing, were distinguished in concentrically zonal segregations according to the results of the mineral and sulfate melt inclusion study by micro‐Raman spectroscopy and SEM‐EDS. We have applied the Raman spectroscopy and first principles calculations to understand structural and vibrational properties of cesanite daughter mineral in polyphase sulfate inclusions. Polarized spectra provided additional information on the overlapped components of the spectral profile. The Raman spectra of cesanite in the range of OH stretching vibrations are reported for the first time. The study aims to clarify the source of the NaSCl‐enrichment in the Udachnaya‐East pipe, which is highly discussed.