수분을 함유한 이산화규소의 한 종류로, 반투명하며 배경색에 따라 다양한 색깔이 변하며 나타나는 보석.
A gemstone consisting of a form of hydrated silica, typically semitransparent and showing many small points of shifting color against a pale or dark ground.
예문:
"The light reflected off the opal, creating a rainbow of colors."
"Australia is the world's leading producer of precious opals."
"An opal's value is often determined by the intensity and variety of its colors."