<?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">porphyry</topic></authority><related type="narrower"><topic>quartz porphyry</topic></related><related type="narrower"><topic>red antique porphyry</topic></related><related type="broader"><topic>igneous rock by composition: physical</topic></related><variant type="other"><topic>lapis porphyrite</topic></variant> <note xml:lang="en"><![CDATA[ A dark purplish-red rock, first quarried in ancient Egypt, containing relatively large crystals in a fine-grained igneous matrix. One of the hardest rocks, it takes a high polish and is valued as a durable sculptor's material and as a decorative architectural material. It is considered the best material for the muller and slab used for grinding artists' colors. ]]></note></mads>