The spelling of the word "semseyite" is quite peculiar. The IPA phonetic transcription of the word is /ˈsɛm.si.aɪt/. The first syllable is pronounced with a short "e" sound, followed by a stressed "s" sound. The second syllable is pronounced with a long "i" sound and the final syllable with a neutral "a" sound. The word refers to a rare mineral composed of lead, copper, and antimony. Despite its unusual spelling, the word is important to earth science and mining industries.