Determination of Fluorine in Geological Samples on the contrAA 800 G Continuum-Source AAS Application Note · contrAA 800 G

Introduction

Fluorine is a common element in the earth’s crust formed in minerals and rocks as fluorides. The abundance of fluorine in the crust averages about 650 ppm (parts per million) and is commonly found in basalts, gabbros, andesites, granodiorites, rhyolites and granites. Marine phosphorites contain significantly higher concentrations of fluorine, averaging more than 30,000 ppm.

Fluorine mineral deposits occur in a wide variety of geological environments and in a multitude of forms associated with or enclosed within volcanic rocks, intrusive igneous rocks, metamorphic rocks or sedimentary rocks. Fluorite (CaF2), the most common and abundant fluorine mineral occurs as vein fillings in rocks that have been subjected to hydrothermal activity and these veins often contain metallic ores which can include sulfides of tin, silver, lead, zinc, copper, and other metals. Fluorite is also found in the fractures and vugs of some limestones and dolomites. Fluorite can be massive, granular or euhedral as octahedral or cubic crystals. Fluorite is a common mineral in hydrothermal and carbonate rocks worldwide.

Fluorite (CaF2), also known as fluorspar in industry, also has important uses in metallurgy including steel production, in the manufacture of ceramics and for the production of hydrofluoric acid as a precursor for other manufactured products. Optical grade fluorite with exceptional clarity is used for lenses in optical system, while specimens with exceptional color are cut into gemstones and ornaments.

In this study, the fluorine content in rock samples was determined by graphite furnace AAS using the contrAA® 800 G High-Resolution Continuum Source Atomic Absorption Spectrometer with solid sampler for direct analysis of finely ground samples.