Alkali basalt glass

Society of Edinburgh that lie had discovered soda in several varieties of Scottish whinstone and m lava from Mt, Aetna (25). He used the term whinstone to include basalt, trap, and certain kinds of porphyry, wacke, and other argillaceous stones. When he analyzed a specimen which had been broken from one of the famous basaltic columns of Staffa, he found that the sum of the earths, silica, and iron never amounted to more than 94 per cent. Suspecting the presence of an alkali, he heated the pulverized mineral with pure sulfuric acid and extracted a salt which he identified as sodium sulfate (25). He proved, moreover, that the sodium compounds had not been dissolved from his glass apparatus. Dr. Kennedy also found 4 per cent of soda in a specimen of lava brought to him by Sir James Hall and Dr. James Home from the famous current of Mt. Aetna which in 1669 had destroyed part of the town of Catania. He published these analyses in 1800 in Nicholsons Journal (25). 

Numerous processes have been proposed for extracting potash from felspar, leucite, alunite, and other minerals rich in this substance, but the cost is so great that very few proposals yet made ofier promise of successful competition with the Stassfurt deposits. This is even the case with alunite, where mere calcination to 1000° drives off water and sulphuric acid, leaving water-soluble potassium sulphate, and alumina. Humphry Davy in his paper On Some Chemical Agencies of Electricity (1807), indicated in Cap. Ill, found that when water was electrolyzed in cavities contained in celestine, fluorspar, zeolite, lepidolite, basalt, vitreous lava, agate, or glass, the bases separated from the acid and accumulated about the cathode. It is therefore probable that if water with finely divided potash minerals in suspension were electrolyzed, the alkali would be separated in a convenient simple way. 

Fig. 18.9 Butcher Ridge at the edge of the polar plateau in the Cook Mountains of southern Victoria Land is composed of highly contorted and layered rocks consisting of glass and apha-nitic rocks ranging from basalt to alkali-rich rhyohte. Although they resemble volcanic rocks, they formed by mixing of melts of basaltic and felsic composition followed by rapid cooling. The petrogenesis of these rocks is not understood. However, they...

Rhyolite is an example of even more siliceous (as much as 70% Si02), or acidic, volcanic material. Rhyolite is a product of rather extreme chemical fractionation relative to the average composition of Earth. It is a common material, but hardly abundant in comparison with basalt, or even andesite. Rhyolitic lavas mainly appear in regions where less extreme types of lavas predominate. Such silica- and alkali-rich materials as rhyolites melt at lower temperatures than basalts or andesites and produce viscous liquids. On cooling, many fail to crystallize, but produce obsidian glass. Some are so forcibly ejected that they erupt as shards of glass, producing widespread falls of volcanic ash and pumice. 

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