opal
Concise Oxford English Dictionary © 2008 Oxford University Press:
opal/ˈəʊpl/
▶noun a gemstone consisting of a quartz-like form of hydrated silica, typically semi-transparent and showing many small points of shifting colour against a pale or dark ground.
– origin C16: from Fr. opale or L. opalus, prob. based on Sanskrit upala ‘precious stone’.
'opal' also found in these Oxford entries:
