False-colour scanning electron micrograph (SEM) of the ceramic material silicon nitride, which is one of the so- called engineering ceramics" used in applications such as novel types of car engines. The unusual appearance of this SEM is due to the use of back- scattered electrons, instead of the usual secondary electrons, to produce the image. These electrons are primary electrons reflected off the specimen, & they can be used to identify a material's constituents. In this micrograph, the white needles are yttrium- silicon oxides, the black needles are the mineral cristobalite, & the dark grey areas are non- crystalline, glassy phases. Magnification: x75 at 35mm size. Gold tint. Original is BW A800/006. Ref: MICROCOSMOS, fig. 8.15, p. 157"