sardonyx
Concise Oxford English Dictionary © 2008 Oxford University Press:
sardonyx /ˈsɑːdənɪks/
▶noun onyx in which white layers alternate with sard.
– origin ME: via L. from Gk sardonux, prob. from sardios ‘sardius’ + onux ‘onyx’.
'sardonyx' also found in these Oxford entries:

