Lignites

C]2Hi50]2. Colourless needles m.pr. 286-288°C. When heated it decomposes into pyro mellitic anhydride, water and CO2. Occurs as the aluminium salt (honeystone) in some lignite beds. Prepared by oxidation of charcoal with concentrated nitric acid. 

Uranium, not as rare as once thought, is now considered to be more plentiful than mercury, antimony, silver, or cadmium, and is about as abundant as molybdenum or arsenic. It occurs in numerous minerals such as pitchblende, uraninite, carnotite, autunite, uranophane, and tobernite. It is also found in phosphate rock, lignite, monazite sands, and can be recovered commercially from these sources. 

Coals (the plural is deliberately used because coal has no defined, uniform nature or structure) are fossil sources with low hydrogen content. The structure of coals means only the structural models depicting major bonding types and components relating changes with coal rank. Coal is classified, or ranked, as lignite, subbituminous, bituminous, and anthracite. This is also the order of increased aromaticity and decreased volatile matter. The H C ratio of bituminous coal is about 0.8, whereas anthracite has H C ratios as low as 0.2. 

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