X-ray Measurements of the Lattice Destruction and Its Recovery on Some Radioactive Minerals*

X-ray measurements were carried out in order to study the spontaneous radiation effects of alianite, gadolinite and monazite on their structures. It was found that the first two gave the experimental evidences of either expan sions from or destruction of their normal lattice structures, while the last one showed lattice expansion only. Heat treatments of these minerals in the vacuum caused them to recover their normal lattice states. Introduction It has long been assumed by mineralogists that the bombardment of alpha-particles, which are liberated in radioactive minerals on disintegration, on their constituent atoms and recoiling of parent atoms are the cause of the metamict states often observed with these minerals. It is also a well-known fact, however, that there are certain minerals such as monazite and autunite, which are radioactive but not found in a metamict state; the fact suggests that there must be some other factors which play important roles in metamictization of radioactive minerals. In fact, several research workers3) 5) 6) 1O) have hitherto given some considerations cn this pro blem and among them Pellas7) 8) reached an important conclusion that the condition prerequisite to metamictization was the existence * A preliminary report of this work was read at the meeting of the Minera logical Society of Japan held in Fukuoka on October 31, 1954. T. UEDA and M. KOREKAWA 199 of partially directed bonds in the structures. Then, Stech9), who studied changes in crystal structures caused by the bombardment of alpha-particles, observed no structure change occurred in crystals with strong bonds and with high degrees of space utilization, and strong columnar ionization by the particles was necessary for struc ture changes. Recently, Hurley and Fairbairn2) on their study on zircon found that the lattice expanded as the metamictization proceeded. The present authors12) also observed the same fact on their study on allanite. gadolinite and monazite. The following report is to deal with this problem of lattice expansion in some metamict minerals with X-ray spectrometric data recently obtained.