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List C - Commodities

List C-1  Commodities
List C-2  Commodity-Related Minerals

General notes
These thesaurus lists, lists A-R, are used by GeoRef indexers for selecting index terms and by searchers for additional information not necessarily found in individual term records in the body of the Thesaurus. In most cases, an hierarchical list is given. In some cases, an alphabetical or other list is provided.

The notes under Searching attempt to guide the searcher in the use of the list. Searchers might also read the notes on Indexing for further clues but should be aware that these notes reflect current practice which in some cases differs from past practice. Further notes on specific terms are in the body of the Thesaurus and additional notes on searching are in the GeoRef Thesaurus, 11th edition Introduction section on searching beginning on page x. Information specific to searching and the individual list topics is included, e.g., a section including commodities begins on page xi.

Under Indexing the current indexing practice is given. These notes should be read along with the instructions under the individual terms in the body of the Thesaurus.

Commodities
Terms in the Commodities list are used for earth materials of actual or potential commercial value, i.e. from an economic viewpoint. Beginning in 1981, new terms were adopted for some commodities, to distinguish between geochemical and economic treatments.
For example, beryllium ores was added in 1981, to be used for economic papers. The existing term, beryllium, was restricted to geochemical use. Where new terms have been added, this is noted in the main body of the Thesaurus. A second list, Commodity-Related Minerals, may be used to relate common economic minerals to their commodity terms.

Special terms for economics and for exploration are indexed with particular commodity groups:
The term economics is used for all of the energy sources and water resources.
For petroleum, petroleum exploration is used.
For coal deposits, coal exploration.
For geothermal energy, geothermal exploration.
For all other nonmetal deposits, and for all of the metal ores, mineral economics and mineral exploration are used.

For papers that are very general or that include a large number of commodities, the commodities may be grouped.
The following terms are general terms to be used as group names: base metals, ceramic materials, construction materials, energy sources, gems, heavy mineral deposits, industrial minerals, metal ores, nonmetal deposits, polymetallic ores, and rare earth deposits.
The group name for oil and gas is petroleum.
Some group names may be autoposted to or indexed with, the specific commodities. Major terms in the commodities list are marked in bold type. The term mineral resources is used for very general papers.

Searching
For complete retrieval, search both specific and general terms.
For example, an exhaustive search on sillimanite deposits could include a search on ceramic materials, excluding andalusite deposits and kyanite deposits.

To isolate economic papers from non-economic, it is advisable to coordinate pre-1981 commodity terms (e.g. beryllium) with the economic geology category codes, see List A, or with ore deposits for metals or deposits for nonmetals. See specific term in the Thesaurus for recommended search strategy. The term metal ores is autoposted to all the specific metal ore terms.

Indexing
In general, the most specific commodity term applicable should be used. Indexers must ensure that a commodity group term is either manually added or will autopost. Where the commodity terms are shown in nonbolded type, e.g. abrasives, it is necessary to index a group name in order to make retrieval of groups possible.

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