margarite
/ˈmɑːɡərʌɪt/noun
1 Mineralogy. A calcium aluminium silicate of the mica group, CaAl4Si2O10(OH)2, usually occurring as minute scales with a pearly lustre. Formerly also called pearl mica.
2 Geology A line of globulites resembling a string of pearls, commonly occurring in glassy igneous rocks.
Origin
Early 19th century. From German Margarit from Hellenistic Greek μάργαρον pearl + German -it.