noun🔗ShareピッチストーンA natural glass, rich in microscopic crystallites, formed by the rapid cooling of lava or magma"The sharp edges of the pitchstone found near the volcano were used by early humans to make tools. "火山近郊で見つかったピッチストーンの鋭い縁は、初期の人類が道具を作るために使用しました。geologymaterialChat with AIVocabulary GamePractice Reading