<descriptor thcode="2"><thesaurus thcode="2" name="USGS Thesaurus" scope="Topics and methods of scientific study carried out by USGS, with product types, scientific disciplines, geologic time, and types of institutional structure and activities.  Broad and shallow, used to help people find scientific information." creator="U.S. Geological Survey" rights="Public domain" edition="2.0" date="2020-01-09" codetype="number" prefix="topic" uri="https://www2.usgs.gov/science/USGSThesaurus" tblname="term" nonpref="nonpref" relterm="relterm" root_code="1" contact="pschweitzer"><category><term thcode="25" code="29" name="distinct labels" parent="26" scope="Preferred labels (descriptor texts) are distinct within the thesaurus. A concept can be specified either by its unique identifier (code) or by the text of its descriptor."/><term thcode="25" code="16" name="hierarchical" parent="11" scope="Substantive broader-narrower relationships exist among the terms."/><term thcode="25" code="13" name="transitive" parent="12" scope="Narrower terms have an &quot;is a&quot; relationship with their broader terms, and generally can be described as part-of, type-of, or instance-of the broader term."/><term thcode="25" code="21" name="disciplines" parent="2" scope="Broad categories of human inquiry or activity, such as scientific disciplines."/><term thcode="25" code="20" name="methods" parent="2" scope="Actions taken to obtain or analyze information"/><term thcode="25" code="19" name="organizational functions" parent="2" scope="Things that organizations do, typically including various types of programs, projects, and services."/><term thcode="25" code="7" name="temporal" parent="2" scope="Terms indicate periods of time, such as chronostratigraphic units, named historical periods or intervals surrounding known historical events, or seasons."/><term thcode="25" code="5" name="theme" parent="2" scope="Terms indicate domains of human concern, such as scientific discipline, societal problems, or characteristics of earth, space, oceans, and living things."/><term thcode="25" code="29" name="distinct labels" parent="26" scope="Preferred labels (descriptor texts) are distinct within the thesaurus. A concept can be specified either by its unique identifier (code) or by the text of its descriptor."/><term thcode="25" code="16" name="hierarchical" parent="11" scope="Substantive broader-narrower relationships exist among the terms."/><term thcode="25" code="13" name="transitive" parent="12" scope="Narrower terms have an &quot;is a&quot; relationship with their broader terms, and generally can be described as part-of, type-of, or instance-of the broader term."/><term thcode="25" code="21" name="disciplines" parent="2" scope="Broad categories of human inquiry or activity, such as scientific disciplines."/><term thcode="25" code="20" name="methods" parent="2" scope="Actions taken to obtain or analyze information"/><term thcode="25" code="19" name="organizational functions" parent="2" scope="Things that organizations do, typically including various types of programs, projects, and services."/><term thcode="25" code="7" name="temporal" parent="2" scope="Terms indicate periods of time, such as chronostratigraphic units, named historical periods or intervals surrounding known historical events, or seasons."/><term thcode="25" code="5" name="theme" parent="2" scope="Terms indicate domains of human concern, such as scientific discipline, societal problems, or characteristics of earth, space, oceans, and living things."/></category><altlabel><altlabel>USGSThesaurus</altlabel><altlabel>USGSThesaurus</altlabel></altlabel></thesaurus><term thcode="2" code="2263" name="platinum-group elements" parent="1426" scope="A group of chemically similar metal elements that tend to occur in the same types of mineral deposits."/><uf><usefor name="PGE"/><usefor name="PGM"/><usefor name="platinum-group metals"/></uf><bt><term thcode="2" code="1426" name="chemical element groups" parent="1382" scope="Groups shown at &lt;http://periodic.lanl.gov/&gt;"/><term thcode="2" code="1382" name="elements" parent="1174" scope="Chemical elements and element groups"/><term thcode="2" code="1174" name="topics" parent="1" scope="Themes, subjects, and concerns for which USGS information resources are relevant."/><term thcode="2" code="1" name="Categories" scope="Thematic terms for categorizing information resources.  This thesaurus is intended to support finding and understanding scientific information."/></bt><rt><term thcode="2" code="1484" name="iridium" parent="1427" scope="Metal element with symbol Ir and atomic number 77 &lt;http://periodic.lanl.gov/77.shtml&gt;"/><term thcode="2" code="1530" name="osmium" parent="1427" scope="Metal element with symbol Os and atomic number 76 &lt;http://periodic.lanl.gov/76.shtml&gt;"/><term thcode="2" code="1534" name="palladium" parent="1427" scope="Metal element with symbol Pd and atomic number 46 &lt;http://periodic.lanl.gov/46.shtml&gt;"/><term thcode="2" code="1538" name="platinum" parent="1427" scope="Metal element with symbol Pt and atomic number 78 &lt;http://periodic.lanl.gov/78.shtml&gt;"/><term thcode="2" code="1559" name="rhodium" parent="1427" scope="Metal element with symbol Rh and atomic number 45 &lt;http://periodic.lanl.gov/45.shtml&gt;"/><term thcode="2" code="1563" name="ruthenium" parent="1427" scope="Metal element with symbol Ru and atomic number 44 &lt;http://periodic.lanl.gov/44.shtml&gt;"/></rt></descriptor>