Category: General

Sedimentary rock consisting of at least 50% calcium carbonate. The term limestone is applied to any sedimentary rock consisting essentially of carbonates. The 2 most important constituents are calcite and dolomite, but small amounts of iron-bearing carbonates might also occur. The oil reservoirs of the Middle East and North Africa contain some 70% of the world’s known oil reserves and about 50% of the world’s natural gas reserves. Most of these are contained in high-energy carbonate platform sediments, or in fractured limestones of large, doubly plunging anticlines

Fuel that contains antiknock, a mixture of the chemicals tetraethyl lead and dibromoethane. The lead from the exhaust fumes enters the atmosphere, mostly as simple lead compounds, poisonous to the nervous systems

A type of coal that contains a lot of moisture and ash and breaks apart easily. Of the four types, lignite has the lowest carbon content and heating value. Lignite is used mainly at electricity-generating plants.

It is the lowest rank of coal, often referred to as brown coal

The removal of readily soluble components, such as chlorides, sulfates, organic matter, and carbonates, from soil by moving ground water