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Kyanoxalite, a new member of the cancrinite group, has been identified in hydrothermally altered hyperalkaline rocks and pegmatites of the Lovozero alkaline pluton, Kola Peninsula, Russia. It was found at Mount Karnasurt (holotype) in association with nepheline, aegirine, sodalite, nosean, albite, lomonosovite, murmanite, fluorapatite, loparite, and natrolite and at Mt. Alluaiv. Kyanoxalite is transparent, ranging in color from bright light blue, greenish light blue and grayish light blue to colorless. The new mineral is brittle, with a perfect cleavage parallel to (100). Mohs hardness is 5-5.5. The measured and calculated densitiesare 2.30(1) and 2.327 g/cm 3 , respectively. Kyanoxalite is uniaxial, negative, ω = 1.794(1), ε = 1.491(1). It is ple ochroic from colorless along E to light blue along O. The IR spectrum indicates the presence of oxalate anions C 2 and water molecules in the absence of C Oxalate ions are confirmed by anion chromatography. The chemical composition (electron microprobe; water was determined by a modified Penfield method and carbon was determined by selective sorption from annealing products) is as follows, wt %: 19.) 0.13 (PO 4 ) 0.09 (OH) 0.01 ] Σ0.68 ⋅ 4.74H 2 O. The idealized formula is Na 7 (Al 5-6 Si 6-7 O 24 )(C 2 O 4 ) 0.5-1 ⋅ 5H 2 O. Kyanoxalite is hexagonal, the space group is P6 3 , a = 12.744(8), c = 5.213(6) Å. The strongest reflections in the X ray powder diffraction pattern are as follows, [d, [A] (I, %)(hkl). According to the X ray single crystal study (R = 0.033), two independent C 2 O 4 groups statistically occupy the sites on the axis 6 3 . The new mineral is the first natural silicate with an additional organic anion and is the most hydrated member of the cancrinite group. Its name reflects the color (κεανος is light blue in Greek) and the species forming role of oxalate anions. The holotype is deposited at the Fersman Mineralogical Museum of the Russian Academy of Sci ences, Moscow, registration no. 3735/1.

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We present a comparative analysis of powder infrared spectra of cancrinite-group minerals with the simplest framework, of AB type, from the viewpoint of crystal-chemical characteristics of extra-framework components. We provide IR spectra for typical samples of cancrinite, cancrisilite, kyanoxalite, hydroxycancrinite, depmeierite, vishnevite, pitiglianoite, balliranoite, davyne and quadridavyne, as well as the most unusual varieties of cancrinite-subgroup minerals (Ca-deficient cancrinite, H 2 O-free cancrinite, intermediate members of the series cancrinite -hydroxycancrinite, cancrinite-cancrisilite, cancrinitekyanoxalite, K-rich vishnevite, S 2 -bearing balliranoite). Samples with solved crystal structures are used as reference patterns. Empirical trends and relationships between some parameters of IR spectra, compositional characteristics and unit-cell dimensions are obtained. The effect of Ca content on stretching vibrations of CO 3 2is explained in the context of the cluster approach. The existence of a hydrous variety of quadridavyne is demonstrated.