<?xml version="1.0" encoding="utf-8"?><!DOCTYPE Zthes SYSTEM "http://zthes.z3950.org/xml/zthes-05.dtd">  <Zthes><term><termId>31471219</termId><termName>perlite</termName><termType>PT</termType><termNote><![CDATA[ A volcanic glass that contains about 75% silica and usually has a higher water content than obsidian; found in Oregon and California. Commercially, the term refers to volcanic glass that will expand or "pop" when heated to form a lightweight aggregate. ]]></termNote><termCreatedDate>2026-03-30 21:06:49</termCreatedDate><relation><relationType>UF</relationType><termId>31471220</termId><termName>calite</termName><termType>ND</termType></relation><relation><relationType>BT</relationType><termId>31457318</termId><termName>volcanic glass</termName><termType>PT</termType></relation></term>  </Zthes>