Kratochvilite is a rare organic mineral formed by combustion of coal or pyritic black shale deposits. It is a hydrocarbon with the formula of either C<sub>13</sub>H<sub>10</sub> or (C<sub>6</sub>H<sub>4</sub>)<sub>2</sub>CH<sub>2</sub>. It is a polymorph of the aromatic hydrocarbon fluorene. It forms white, yellow to brown crystals in the orthorhombic system which occur often as a 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. It is named after Josef KratotchvÃÂl, Czech geologist.