Analysis of the dusty soil by Viking and Pathfinder lander instruments showed the principal constituent materials (in oxide forms by weight) to be silicon (SiO2; 46 percent), iron (Fe2O3; 18 percent), aluminum (Al2O3; 8 percent), magnesium (MgO; 7 percent), calcium (CaO; 6 percent), sulfur (SO3; 5.4 percent), sodium (Na2O; 2 percent), and potassium (K2O; 0.3 percent).
Slag leaves the furnace by the same taphole as the iron (upon which it floats), and its composition generally lies in the range of 30 40 percent silica (SiO2), 5 15 percent alumina (Al2O3), 35 45 percent lime (CaO), and 5 15 percent magnesia (MgO).
This spinel mineral is ideally composed of ferrous oxide and chromic oxide with the chemical composition FeO · Cr2O3, but it is often found in nature with magnesia (MgO) substituting for FeO and alumina (A12O3) or ferric oxide (Fe2O3) substituting for Cr2O3.
Adding burnt dolomite (CaO·MgO) results in a magnesia (MgO) content in the slag of about 6 percent, thereby decreasing slag corrosion of the magnesite lining.
Magnesia brick is made from periclase, the mineral form of magnesia (MgO).
In examinations of the stability fields of MgSiO3 (enstatite), MgSiO3 is normally used as the component rather than the three elements, Mg, Si, and O, or the two oxides, MgO and SiO2.
The magnesia (magnesium oxide, MgO) content of raw materials must be low because the permissible limit in portland cement is 4 to 5 percent.
For example, one mole of SiO2 is combined with one mole of MgO to make the magnesium-rich pyroxene, MgSiO3 (enstatite): SiO2 + MgO → MgSiO3.
The major oxides of the rocks generally correlate well with their silica content: those rocks with low silica content are enriched in magnesium oxide (MgO) and iron oxides (FeO, Fe2O3, and Fe3O4) and are depleted in soda (Na2O) and potash (K2O); those with a large amount of silica are depleted in magnesium oxide and iron oxides but are enriched in soda and potash.
The reaction curves for Al2SiO5 and for muscovite + quartz ←→ potassium-feldspar + sillimanite + H2O are significant in metamorphic rocks that have a high aluminum oxide (Al2O3) content as compared to other components (e.g., calcium oxide [CaO], magnesium oxide [MgO], and ferrous oxide [FeO]).
In addition, they can be classified as either acidic (containing silica [SiO2] or zirconia [ZrO2]) or basic (containing alumina [Al2O3] or alkaline-earth oxides such as lime [CaO] or magnesia [MgO]).
