Unusually, phonolite forms from magma with a relatively low silica content, generated by low degrees of partial melting ( less than 10 % ) of highly aluminous rocks of the lower other silica crystals, and is dominated by low-silica feldspathoid minerals more than feldspar minerals.
22.
Constituents that are permitted in Portland-composite cements are artificial pozzolans ( blastfurnace slag ( in fact a latent hydraulic binder ), silica fume, and fly ashes ) or natural pozzolans ( siliceous or siliceous aluminous materials such as volcanic ash glasses, calcined clays and shale ).
23.
His account of the aluminous district of Tolfa and adjacent hills, published in 1786, gained for him the notice of the king of Naples, who invited him to inspect the, mines and similar works in that kingdom, and appointed him professor of mineralogy to the royal artillery.
