<?xml version="1.0" encoding="utf-8"?><!DOCTYPE Zthes SYSTEM "http://zthes.z3950.org/xml/zthes-05.dtd">  <Zthes><term><termId>31457381</termId><termName>Potomac breccia</termName><termType>PT</termType><termNote><![CDATA[ A striking breccia quarried in the Blue Ridge Mountains in Maryland and Virginia; it consists mostly of limestone, quartz pebbles, and multicolored fragments ranging from sand grains to cobbles, all cemented together in a calcareous matrix. It can be extremely difficult to work as the hard pebbles tend to break away from the softer matrix. ]]></termNote><termCreatedDate>2026-03-30 21:03:06</termCreatedDate><relation><relationType>UF</relationType><termId>31457382</termId><termName>Potomac marble</termName><termType>ND</termType></relation><relation><relationType>UF</relationType><termId>31457383</termId><termName>Potomic breccia</termName><termType>ND</termType></relation><relation><relationType>UF</relationType><termId>31457384</termId><termName>breccia, Potomac</termName><termType>ND</termType></relation><relation><relationType>UF</relationType><termId>31457385</termId><termName>calico marble</termName><termType>ND</termType></relation><relation><relationType>UF</relationType><termId>31457386</termId><termName>calico rock</termName><termType>ND</termType></relation><relation><relationType>UF</relationType><termId>31457387</termId><termName>marble, Potomac</termName><termType>ND</termType></relation><relation><relationType>UF</relationType><termId>31457388</termId><termName>marble, calico</termName><termType>ND</termType></relation><relation><relationType>UF</relationType><termId>31457389</termId><termName>rock, calico</termName><termType>ND</termType></relation><relation><relationType>BT</relationType><termId>31438553</termId><termName>breccia</termName><termType>PT</termType></relation></term>  </Zthes>