At present, the vesuvianite group of minerals consists of eight members, six of which are distinguished by the dominant cation in the Y1(A,B) five-coordinated site. We investigated two vesuvianite samples from the type locality by electron microprobe analysis, Mössbauer and infrared spectroscopy, TGA/DSC, MAS NMR, single-crystal and powder X-ray diffraction. The crystal structures of these samples (# 27844 and 51062 from the Vesuvius collection, Fersman Mineralogical Museum, Moscow) have been refined to R₁ = 0.027 and R₁ = 0.035, respectively. Both samples have the space group P4/nnc; a = 15.5720(3) and 15.5459(3), c = 11.8158(5) and 11.7988(4), respectively. In both samples low-occupied T1 and T2 sites are populated by minor B and Al, which agrees with their high-temperature origin. According to our experimental results, the general revised crystal-chemical formula of vesuvianite can be written as^VII−IXX₁₉ ^VY₁ ^VIY₁₂(Z₂O₇)₄(ZO₄)₁₀(W)₁₀, where X are seven-to nine-coordinated sites of Ca with minor Na, K, Fe²⁺ and REE impurities; VY has a square pyramidal coordination and is occupied predominantly by Fe³⁺ with subordinate Mg, Al, Fe²⁺ and Cu²⁺; VIY has octahedral coordination and is predominantly occupied by Al with subordinate Mg, Fe²⁺, Fe³⁺, Mn²⁺, Mn³⁺, Ti, Cr and Zn; ZO₄ = SiO₄, sometimes with subordinate AlO₄ and/or (OH)₄, and W = OH, F, with minor O and Cl. The idealized charge-balanced formula of the vesuvianite end-member without subordinate cations is Ca₁₉Fe³⁺(Al₁₀Me²⁺ ₂)(Si₂O₇)₄(SiO₄)₁₀O(OH)₉, where Ме = Fe²⁺, Mg²⁺, Mn²⁺.