Karpatite from the Picacho Peak Area, San Benito County, California, has been characterized as an exceptionally pure crystal of coronene (C24H12) by infrared absorption analysis, Raman scattering analysis, and differential thermal analysis. Furthermore, the crystal structure of karpatite was determined using a single-crystal X-ray diffraction method for the first time. The mineral crystallizes in the monoclinic system, space group P21/a, with unit-cell dimensions of a = 16.094(9), b = 4.690(3), c = 10.049(8) Å, β = 110.79(2)°, V = 709.9(8) Å3, and Z = 2. The structure was solved and Finally refined to R1 = 3.44% and wR2 = 2.65%, respectively. The coronene molecules in the crystal structure of karpatite are all isolated and the intermolecular distances correspond to van der Waals interactions. The coronene molecules have the high degree of aromaticity and no overcrowded hydrogen atoms, both of which avoid a mixing of other polycyclic aromatic hydrocarbons (PAHs) in karpatite. The corrugated arrangement of coronene molecules constituting karpatite prevents intercalation reactions, accounting for the exceptional purity of this mineral.