CHARACTERIZATION OF FIBROUS ZEOLITES FROM WESTERN NORTH DAKOTA

The fibrous zeolite erionite has been of interest due to its potential for causing pleural diseases in humans. We have carried out sampling of rock and/or soil from 27 locations in western North Dakota to characterize fibrous zeolite occurrences. Sampled areas include the North and South Killdeer Mountains in Dunn County, West and East Rainy Buttes in Slope County, and White Butte, also in Slope County. Samples were disaggregated, and fine grained material was collected by vacuum filtration after water column settling. Of 37 samples tested by powder XRD, 17 tested positive for zeolitic material. Nine samples that showed the strongest zeolite patterns were analyzed using SEM/EDS and EMPA. In some cases the identical fibers were analyzed using both methods. From the 9 samples, 28 individual fibers (77 points) were examined. SEM/EDS analyses plot as both erionite and offretite on a Mg - Ca(+Na) - K(+Ba+Sr) diagram. EMP analysis showed most analyzed fibers plotted as offretite, and did not meet the criteria for identification as erionite based on Dogan and Dogan (2008) Environ Geochem Health 30:355. These results raise the question of whether the chemical composition and/or crystal structure of offretite create a similar health concern as erionite. Ongoing and future work includes crystallographic investigation and regional and local stratigraphic correlation into Montana and South Dakota.

Acknowledgment: NIH grant P20 RR016471 from INBRE/NCRR.