Jasper Jasper Jasper, an aggregate of microgranular quartz and/or chalcedony and other mineral phases, is an opaque, impure variety of silica, usually red, yellow, brown or green in color; and rarely blue. The common red color is due to iron(III) inclusions. The mineral aggregate breaks with a smooth surface and is used for ornamentation or as a gemstone. It can be highly polished and is used for items such as vases, seals, and snuff boxes. The specific gravity of jasper is typically 2.5 to 2.9. A green variety with red spots, known as heliotrope (bloodstone), is one of the traditional birthstones
Aluminium alloy inclusions where carbon anodes and cathodes are in contact with the mix. Later in the process, any carbon tools in contact with the liquid aluminium can react and create carbides. In aluminium alloys containing magnesium, magnesium oxides (MgO), cuboids (MgAlO-cuboid) and metallurgical spinel (MgAl2O4-spinel) can form. They result from the reaction between magnesium and oxygen in the melt. More of them will form with time and temperature. Spinel can be highly detrimental because of its big size and high hardness. Particles of refractory material in contact with aluminium can detach and become inclusions. We can find graphite inclusions (C), alumina inclusions