Cloudiness in Zircons - A Chemical and Morphological Study

Electron microprobe and infrared spectroscopic studies show that the clouded areas in zircons contain additional Fe₂O₃, CaO, MgO, Al₂O₃ and water than those of the clear areas. IR spectroscopic analysis indicates that the clouded portions have both molecular H₂O and OH molecule in similar proportions. Total amount of water in the clouded portions is of the order of 8% by weight. There is a direct relationship between water+secondary components and cloudiness of the zircons. The data suggest that F₂O₃, CaO, MgO and Al₂O₃ dissolved in water got incorporated into the crystal structure of zircon and replaced ZrO₂ and SiO₂ simultaneously.