Stereoscan 360 scanning electron microscope, equipped with an Oxford Inca Energy 200 EDS for microanalysis and a Pentafet detector and an ultrathin window for the determination of elements with atomic number down to boron. All spectra were obtained at 15 kV accelerating voltage, 25 mm working distance, and 1 µA probe current for 60 to 300 seconds. Primary standardization was performed on SPI Supplies and Polaron Equipment analytical standards. Daily standardization was performed on a high-purity metallic cobalt standard.