In this study, we present Raman spectra of pure synthetic hydrothermal orthorhombic Na₂Ca(CO₃)₂ carbonate together with naturally occurring orthorhombic nyerereite (Na,K)₂Ca(CO₃)₂ and hexagonal gregoryite (Na,K,Ca_x)_2-x(CO₃) from Oldoinyo Lengai natrocarbonatites (Tanzania) to show the diversity of spectra and permit the use of Raman spectroscopy to identify these minerals in small inclusions. Synthetic orthorhombic Na₂Ca(CO₃)₂ carbonate has only one type of Raman spectrum, which is independent of the crystallographic orientation. The Raman spectra of nyerereite can be divided into three types, depending on intensity of symmetric stretching ν₁(CO₃)²⁻ vibrations in region 1070–1090 cm⁻¹. All these nyerereite types have identical chemical compositions; thus, the differences in Raman spectra are likely to be related to crystallographic orientations. Some nyerereite Raman spectra can be erroneously interpreted as gregoryite because of similarity in peak position of strong ν₁(CO₃)²⁻ band. However, the diagnostic features of the gregoryite Raman spectrum can be summarized as follows: (1) presence of a symmetric peak attributed to ν₁(CO₃)²⁻ vibrations at 1078 cm⁻¹; (2) presence of one broad band ν₄(CO₃)²⁻ with a peak position at 702–707 cm⁻¹; (3) a stronger band ν₁(SO₄)²⁻ that occurs at 1003–1006 cm⁻¹ and the presence of additional weaker bands ν₂(SO₄)²⁻ and ν₄(SO₄)²⁻ at 460–462 and 630–635 cm⁻¹; and (4) a ν₁(PO₄)³⁻ band that appears at 952–954 cm⁻¹. Incorporation of significant amounts of additional cations (up to 0.5 apfu) and particularly K (up to 0.4 apfu) in natural nyerereites leads to a change in the commensurately modulated structure of pure Na₂Ca(CO₃)₂ (P2₁ca), which becomes an incommensurately modulated structure (less ordered) with space group Cmcm; and these changes are reflected in a reduction of the number of Raman bands in symmetric stretching ν₁(CO₃)²⁻ and inplane bending ν₄(CO₃)²⁻ vibration regions or even the complete absence of the Raman bands in antisymmetric stretching ν₃(CO₃)²⁻ and 2*ν₂(CO₃)²⁻ vibration regions compared with pure Na₂Ca(CO₃)₂.