I've mostly heard people say that there "wasn't a scintilla of intelligence or emotion" in the eyes of someone or something. That's a bit rude, though indisputably accurate at times, because a scintilla is the barest spark or trace of something. Sometimes there really isn't a trace, a particle, an iota, jot, whit, speck, or bit of anything happening upstairs.
Perhaps you may have heard of scintilla's cousin, scintillating, as in a conversation that is sparklingly brilliant and witty, or the sun scintillating on the waves. Both are fun to use and can be either earnest or sarcastic, which I think is accommodatingly versatile of them. (An absolutely dripping "scintillating" when someone tells a boring story is such a move.)
Go ahead and try them in conversation without a scintilla of doubt in your heart.
–C