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Some of our finest [ about ] Approved Articles (107) Developed Articles (over 900) "Knowledge is the true organ of sight, not the eyes." —From the Panchatantra (Indian literature) Article of the Week [ about ] (PD) Photo: U.S. Geological Survey / Andrew Silver Anthracite coal (coin shown for scale). Coal is a carbon-containing rock formed by the debris from the decay of ferns, vines, trees and other plants which flourished in swamps millions of years ago. Over time, the debris became buried and the actions of bacteria, heat and pressure transformed the debris first into peat (a precursor of coal) and then into the various types of coal as we know them today. In more technical terminology, that process of transformation is referred to as metamorphosis, coalification or lithification. Coal is extracted by mining from deposits that exist deep underground as well as deposits that are essentially at or near the surface of the ground. Because of the various degrees of transformation that occurred during the forming of coal deposits in different locations, the composition of coal varies from one deposit to another. No two coals are the same in every respect. In general, coal consists of carbon, hydrogen, oxygen, nitrogen, sulfur and mineral matter (including compounds of silicon, aluminum, iron, calcium, magnesium and others).[more...] New Draft of the Week [ about ] Gasoline or petrol is a fuel, derived from petroleum crude oil, for use in spark-ignited internal combustion engines. Conventional gasoline is mostly a blended mixture of more than 200 different hydrocarbon liquids ranging from those containing 4 carbon atoms to those containing 11 or 12 carbon atoms. It has an initial boiling point at atmospheric pressure of about 35 °C (95 °F) and a final boiling point of about 200 °C (395 °F). Gasoline is used primarily as fuel for the internal combustion engines in automotive vehicles as well in some small airplanes. In Canada and the United States, the word "gasoline" is commonly used and it is often shortened to simply "gas" although it is a liquid rather than a gas. In fact, gasoline-dispensing facilities are referred to as "gas stations". Most current or former Commonwealth countries use the term "petrol" and their dispensing facilities are referred to as "petrol stations". The term "petrogasoline" is also used sometimes. In some European countries and elsewhere, the term "benzin" (or a variant of that word) is used to denote gasoline. In aviation, "mogas" (an abbreviation for "motor gasoline") is used to distinguish automotive vehicle fuel from aviation fuel known as "avgas".[more...]