From Longman Dictionary of Contemporary Englishstony-facedˌstony-ˈfaced (also stone-faced) adjective EMOTIONALUNFRIENDLYshowing no emotion or friendliness Tony stared at me in stony-faced silence.
Examples from the Corpus
stony-faced• Normally, any ordinary citizen subject to dropped charges would receive a stony-faced apology and the opportunity to leave via the public foyer.• Dad gazed with stony-faced approval at the walnut dash, jewelled with clocks and dials.• A stony-faced Barnes retreated behind the scenery.• A stony-faced Mr Mugabe came in an open-roofed Bentley.• Instead, his two stony-faced sisters, who had never approved of him, led the mourners with their husbands. 