Microdiamond. Coloured scanning electron micrograph (SEM) of a dodecahedral (twelve- faced) microdiamond crystal from Siberia, Russia. Microdiamonds are diamonds (pure crystals of carbon) which measure less than half a millimetre in any dimension. They are being studied as an alternative to the more expensive larger diamonds used in industry, for instance as abrasives or heat dissipators. Microdiamonds are thought to form either with larger diamonds in the Earth's mantle (the layer beneath the crust), or in the ascending magma (molten rock) that can bring the larger stones to the surface. Magnification: x120 at 6x7cm size. x200 at 4x5"~LANDSCAPE"