Other minerals such as topaz contain fluorine. Fluorides, unlike other halides, are insoluble and do not occur in commercially favorable concentrations in saline waters.  Trace quantities of organofluorines of uncertain origin have been detected in volcanic eruptions and geothermal springs.  The existence of gaseous fluorine in crystals, suggested by the smell of crushed antozonite , is contentious;   a 2012 study reported the presence of % F
2 by weight in antozonite, attributing these inclusions to radiation from the presence of tiny amounts of uranium .