Mineralogical purity

The crystallites in alumina ceramics are mainly oc-A1203, mineralogically known as corundum (a synonym for sapphire). Corundum is 9 on the Mohs scale of hardness, i.e. it is next hardest to diamond, at 10. Examples of the micro structures of a high-purity alumina and a debased alumina are shown in Figs 5.20(a) and 5.20(b) respectively. The latter consists of a-Al203 crystallites embedded in a glass-crystalline matrix usually composed of calcium and magnesium silicates. 

Although uncommon, workable deposits of magnesium hydroxide (known mineralogically, as brucite) occur in several parts of the world, especially the United States and China. Some of these are relatively pure, and after milling and beneficiation processes, appear capable of producing material of filler-grade purity and size. Despite... 

Steatite - This originally was a mineralogical name applied to pine talc. Today it refers to high-purity, dense, very fine-grained talc that can be machined. On firing, it has good electrical insulating properties and is used in the manufacture of electrical porcelain. 

Researchers [36, 38] have characterized NaOH activated fly ash residues (zeolites) and have ascertained their highly zeolitic nature [7]. It has also been opined [37,39] that the purity of these residues is mainly decided by their cation exchange capacity, mineralogy and morphology. However, study of pore characteristics (viz., size and volume) of such residues has not been explored in detail. 

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