Definition of mackayite in English:

mackayite

Pronunciation /məˈkʌɪʌɪt/ /ˈmakiʌɪt/

noun

Mineralogy
  • A green, tetragonal, hydrated tellurite of ferric iron, FeTe₂ O₅ (OH), occurring as pyramidal to short prismatic crystals.

Origin

1940s. From the name of John W. Mackay + -ite.