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 (alpha-AlO), CaO, SiO, … After some time, graphite refractory in contact with aluminium will react to create aluminum carbides (harder and more detrimental inclusions). In aluminium alloy containing magnesium, the magnesium reacts with some refractories to create rather big and hard inclusions similar to spinels. Unreacted refractory particles coming from the degradation of refractory materials which comes in contact with the melt. Chloride inclusions (MgCl, NaCl, CaCl, …) are a special type of inclusion as they are liquid in liquid metal. When aluminium solidifies, they form spherical voids similar to hydrogen gas porosity but the void contains a chloride crystal