Kratochvilite is a rare organic mineral formed by combustion of coal or pyrite, pyritic shale, black shale deposits. It is a hydrocarbon with the formula of either C₁₃H₁₀ or (C₆H₄)₂CH₂. It is a polymorph of the aromatic hydrocarbon fluorene. It forms white, yellow to brown crystals in the orthorhombic Crystal system, system which occur often as a Druse (geology), druzey encrustation. It has a specific gravity of 1.21 and a Mohs hardness of 1 to 2. It was first described from the Nejedly mine in Bohemia, Czech Republic in 1937.

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Organic minerals Minerals described in 1937 {{mineral-stub