cristobalite
Concise Oxford English Dictionary © 2008 Oxford University Press:
cristobalite /krɪˈstəʊbəlʌɪt/
▶noun a form of silica which is the main component of opal.
– origin C19: named after Cerro San Cristóbal in Mexico, where it was discovered.
'cristobalite' also found in these Oxford entries:

