Economic Mineral Deposits: Coal and Petroleum

Fundamental vocabulary terms and definitions regarding economic mineral deposits, coal ranks, coal formation, and petroleum properties and origin based on lecture notes.

Ore Mineral

A mineral which contains a metallic element in a quantity that can be exploited and extracted for use at an economical cost.

Bauxite

An oxide of aluminum from which the metal can be recovered by electrolytic refining at an economic cost, qualifying it as an ore.

Ore Deposit

A natural concentration of an ore mineral in a massive rock body that is of considerable size and volume, often in terms of millions of tons.

Gangue Minerals

Non-metallic minerals found associated with an ore mineral that are considered worthless and must be separated before metal extraction.

Quartz

A common gangue mineral associated with many metallic ore minerals, with the chemical formula $SiO_2$.

Coal

A solid stratified rock or sedimentary formation of highly carbonaceous character derived from vegetable matter through burial, compaction, and biochemical transformation.

Coke

A converted variety of coal produced by heating coal to a very high temperature in an air-free atmosphere.

Peat

The first stage of transformation to coal, consisting of partly changed vegetable matter where original structure is easily visible.

Bog Peat

A type of peat evolved out of lower types of vegetation, such as mosses.

Mountain Peat

A decomposed and partially altered form of higher types of trees found in submountainous regions.

Lignite (Brown Coal)

The lowest rank of coal, variously colored and earthy in texture, with a typical calorific value between $9000$ and $12,500\,B.Th.U$.

Bituminous Coals (Common Coal)

The most common commercial coal variety where original vegetable matter has fully transformed into a hard, brittle, and compact mass.

Vitrain

A band in bituminous coal characterized by a glassy luster, shining like glass, and small thickness.

Clarain

Brittle, duller bands in bituminous coal that contain vegetable matter in an easily recognizable structure and often show fine lamination.

Durain

A typically dull, lusterless variety of bituminous coal showing a rough irregular fracture.

Fusain

A band of friable granular mass in coal that contains woody fibrous tissues visible under a microscope.

Caking Coals (Coking Coals)

Bituminous coals rich in volatile matter and poor in moisture and sulphur that yield high-heating value coke when heated without air.

Anthracite

The highest rank of coal, characterized by being very hard, jet black, and possessing a metallic luster; it burns with a blue flame.

Cannel Coal

A type of bituminous coal exceptionally rich in plant spores and resins that burns with a luminous flame.

Boghead Coal

A variety of Cannel Coal in which algal remains dominate over spores and resins.

Humic Sediment

Source material for coal derived from higher vegetation (herbs, shrubs, trees) rich in cellulose ($50$-$70\%$) and protein ($10$-$15\%$).

Sapropelic Sediments

Source material for coal comprising chiefly planktonic algae found submerged at the bottom of lakes and seas.

Bio-chemical Decomposition

A process involving bacteria that breaks down the organic matter of wood into coal constituents.

Dynamo-chemical Transformation

The alteration of coal structure into more compact, metamorphosed varieties under the influence of temperature and pressure.

Lower Gondwana Coals

Indian coal deposits of Permian age that account for $98\%$ of annual production, mainly consisting of bituminous types derived from Glossopteris vegetation.

Tertiary Coals

Coal deposits in India found in states like Assam and Arunachal Pradesh, often high in volatile matter and used in the chemical industry.

Petroleum

Commonly known as mineral oil or crude oil, it is a complex mixture of hydrocarbons occurring in liquid form within the earth's surface rocks.

Paraffins

A series of hydrocarbons that are main constituents of crude oil, including methane, ethane, propane, and butane.

Natural Gas

Gaseous hydrocarbons often associated with petroleum, primarily consisting of the paraffin group and low-boiling liquid hydrocarbons like pentane and hexane.

Organic Theories of Petroleum

The generally accepted view that oil was formed from huge accumulations of organic matter (vegetable and animal) via bacterial and chemical decomposition.

Anaerobic Environments

Oxygen-free conditions, such as stagnant branch of seas or gulfs, considered ideal for the evolution of oil from organic debris.

Reservoir Rocks (Pools)

Sedimentary formations where petroleum currently occurs, which may be located at large distances from the original site of formation.

Interface Capture

A migration process where oil-mixed water is expelled from a compacting clay bed into a neighboring sand layer, where the oil is retained.