α.   1500s Guilhelmyte,   1500s 1800s– Guilhelmite,   1600s– Guilielmite,   1700s– Guilelmite,   1700s– Guillemite  Brit. /ˈɡɪləmʌɪt/, U.S. 
/ˈɡɪləˌmaɪt/,   1800s– Guillelmite,   1900s– Guillielmite. 
β. 1600s Guilliammit, 1600s 1800s–1900s Guilliamite.