<?xml version="1.0" encoding="utf-8"?><metadata xmlns:dc="http://purl.org/dc/elements/1.1/"  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:dcterms="http://purl.org/dc/terms/"><dc:title xml:lang="en">cation-ratio dating</dc:title><dc:identifier>http://AATesaurus.cultura.gencat.cat/aat/getty_en?tema=31341244</dc:identifier><dc:language>en</dc:language><dc:publisher xml:lang="en">Getty Institute</dc:publisher><dcterms:created>2026-03-30 20:32:02</dcterms:created><dcterms:isPartOf xsi:type="dcterms:URI">http://AATesaurus.cultura.gencat.cat/aat/getty_en</dcterms:isPartOf><dcterms:isPartOf xml:lang="en">Tesaurus d&apos;Art i Arquitectura</dcterms:isPartOf><dc:format>text/html</dc:format> <dcterms:alternative xml:lang="en">dating, cation-ratio</dcterms:alternative> <dc:description xml:lang="en"><![CDATA[ Cation-ratio dating involves the analysis of biogenic rock varnish, a micrometer-thick coating of manganese, silicon, aluminum and iron, believed to age predictably and thus serve as a chronometer. In particular, the ratio of certain cations, (calcium + potassium)/titanium, has been posited to decrease as the varnish ages. In recent decades, some scholars have challenged these assumptions and questioned the usefulness of the technique as a reliable way to date lithic artifacts.  ]]></dc:description></metadata>