<?xml version="1.0" encoding="utf-8"?><mads xmlns="http://www.loc.gov/mads/" xmlns:mods="http://www.loc.gov/mods/v3" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.loc.gov/mads/
mads.xsd"><authority><topic authority="http://AATesaurus.cultura.gencat.cat/aat/getty_en">quartz porphyry</topic></authority><related type="narrower"><topic>elvan</topic></related><related type="broader"><topic>rhyolite</topic></related><related type="broader"><topic>porphyry</topic></related><variant type="other"><topic>porphyry, quartz</topic></variant><variant type="other"><topic>quartz-porphyry</topic></variant> <note xml:lang="en"><![CDATA[ A porphyritic rhyolite containing phenocrysts of quartz and alkali feldspar in a microcrystalline or cryptocrystalline groundmass. ]]></note></mads>