A treatise on the building and ornamental stones of Great Britain and foreign countries : arranged according to their geological distribution and mineral character, with illustrations of their application in ancient and modern structures (1872)
Hull, Edward, 1829-1917, author · London : Macmillan and Co. · leaf 128
94 LAVAS. dine, it becomes trachyte porphyry, of which there are examples in Cos. Antrim and Down, in Ireland. In the trachyte of the Drachenfels, oligoclase accom- panies sanidine as a constituent, with magnesia-mica, and hornblende.1 The varieties of this rock, conse- quent on changes in chemical… … MAGNIFIED SECTION OF TRACHYTE FROM PUY CAPUCIN (a. V. LASAULX). resembling granite, on the other we find the same constituents passing into obsidian (or volcanic glass), or pumice-stone so porous as to float on water. In this condition it passes beyond the category of build- ing stones, and…
Building stones
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