Warwickite from Edwards, St. Lawrence County, NY (05.02.2012)
We report here the second occurrence of warwickite in New York, the first occurrence of boron minerals (excluding tourmaline) in the Adirondack Lowlands, and the closest composition to the theoretical warwickite ever reported.
During the mineralogical survey of the mineral specimens from the New York State Museum Collections we found that one specimen from the Edwards Mine, St. Lawrence County, (NYSM 13164) contains warwickite (green on the photograph), spinel (pink, containing up to 2% Cr2O3), anhydrite, dolomite, calcite, and pyrite. Warwickite, analyzed by electron microprobe, yielded the following composition: Cr2O3 0.88 TiO2 21.85 MnO 0.09 Al2O3 6.99 ZrO2 0.81 MgO 43.77 B2O3 26.04, all oxides in wt. % with sum 100.43 (B2O3 calculated for 3 B apfu). This corresponds to the empirical formula Cr0.02 Ti0.37Al0.18Zr0.01Mg1.45B1.00O4 or ideally Mg1.5 Ti0.5 BO4.