FTIR spectroscpy of natural fluorite from Ambadongar, Gujarat

The principal aim of this study is to examine the presence of structural water in the form of a hydrous ion (OH-) in fluorites of Ambadongar, Gujarat. Several recent spectroscopic studies indicate that in addition to molecular water in fluid inclusions of fluorite, structurally bound water may occur as H₂O and OH species in hydrothermal fluorite. To further clarify this effect, a FTIR study has been carried on hydrothermal fluorite samples from Ambadongar. The analysis were carried out at room temperature as well as 250°C on powdered samples of yellow, blue-green, blue and colourless fluorites. FTIR spectroscopic measurements of all the fluorites show a broad absorption band between 3439–3410 cm^?1 corresponding to bond of O-H stretching vibration indicating the presence of structurally bound water in all fluorites. This structural water in variable amount as different hydrous species associated with other impurity may act as an energy absorbent in the crystal and production of colour in fluorites. From field study of fluorite veins the colour was determined as blue and purple, which, are commonly inter layered, followed by white, finally yellow and colourless varieties.