Monazite is commonly believed to be a nonmetamict mineral. The results of the published X-ray examination of monazite do not
unambiguously support this belief. The results of the present investigation on four different samples of monazite of known
thorium content show that the thorium-containing monazite occur in a fairly high degree of metamictization. The results of
the petrological examination also support this conclusion.
Communicated by Prof. H. J. Bhabha