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| Mineral | 12 | Any of various naturally occurring homogeneous substances (such as stone, coal, salt, sulfur, sand,... | ^ |
| FossilFuel | 5 | FossilFuel is the subclass of Fuel whose instances are derived from fossilized organic deposits... | ^ |
| Rock | 7 | Rock is any naturally formed aggregate of one or more minerals, consolidated or not, with some de... | ^ |
| Coal | 1 | Coal is a black or brownish black solid combustible substance formed by the partial decomposition... | ^ |
| BrownCoal | . | BrownCoal is a soft Coal harder than peat and softer than bituminous coal. Also called lignite,... | ^ |
