<?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</topic></authority><related type="narrower"><topic>amethyst</topic></related><related type="narrower"><topic>chalcedony</topic></related><related type="narrower"><topic>chert</topic></related><related type="narrower"><topic>quartz crystal</topic></related><related type="narrower"><topic>aventurine</topic></related><related type="narrower"><topic>rose quartz</topic></related><related type="narrower"><topic>citrine</topic></related><related type="narrower"><topic>cristobalite</topic></related><related type="broader"><topic>mineral</topic></related><related type="broader"><topic>gemstones by specific type</topic></related><related type="broader"><topic>silicates</topic></related> <note xml:lang="en"><![CDATA[ The most common variety of silica; commonly occurs as crystals. ]]></note></mads>