The word "riopel" is an uncommon term used in geology to refer to a type of quartz-rich rock formation. It is pronounced as /riːoʊpel/ in IPA phonetic transcription. The spelling of this word is based on its French origin and the usage of the letters "io" as a diphthong. The pronunciation features a long "e" sound followed by a stressed "o" sound and a final "pel" sound. The word is not commonly known, but it remains an important term for those studying rock formations.