They are formed of trachyte, dolerite and basalt.
Large areas are overlain with trachyte, basalt, obsidian, tuff and pumice.
The most conspicuous features of the entire region, Mount Ararat (16,930 ft.) and Mount Alagoz (13,440 ft.), are both solid masses of trachyte; and both rise above the limits of perpetual snow.
Like the rest of the cluster, the island is of volcanic origin, with tuff, trachyte and obsidian among its ordinary rocks.
North-west of Milo, is an uninhabited mass of trachyte, often called Eremomilo or Desert Melos.
Included in this group are some rocks which are more properly to be regarded as vitreous forms of trachyte than as glassy rhyolites (Iceland), but except by chemical analyses they cannot be separated.
The mountain is quarried, and from 1267 onward supplied stone (trachyte) for the building of Cologne cathedral.
Such rocks as basalt, diorite and trachyte are comparatively rare.
They are, first, plutonic rocks, especially granite; secondly, volcanic rocks, chiefly trachyte and dolerite; and thirdly, palaeozoic schists.
The Nahuatl lapidaries had at hand many varieties of workable and beautiful stone - onyx, marble, limestone, quartz and quartz crystal, granite, syenite, basalt, trachyte, rhyolite, diorite and obsidian, the best of material prepared for them by nature; while the Mayas had only limestone, and hard, tenacious rock with which to work it, and timber for burning lime.
The trachyte of Cabo de Gata in south-east Spain, which contains 12-15% of phosphoric acid.
Many of the oceanic islets are composed of coral limestone, which in this way becomes phosphatized; others are igneous, consisting of trachyte or basalt, and these rocks are also phosphatized on their surfaces but are not so valuable, inasmuch as the presence of iron or alumina in any quantity renders them unsuited for the preppration of artificial manures.
The country generally is of sandstone or granite formation, with occasional trachyte and basaltic ranges.
With the exception of the coral and a small amount of calcareous sandstone, the rocks are entirely volcanic and range from basalt to trachyte, but are mainly basalt.
Of the best rubble masonry, an ashlar floor of blocks of close-grained trachyte being laid directly under the bridge, where the action was severest.
The bulk of the mountain consists of andesite, but porphyry, obsidian, trachyte, basalt, and.
It is formed of basalt, trachyte and phonolite, and the soil is very fertile.
In the south of the island there are sills and dykes of felsite, quartz-porphyry, rhyolite, trachyte and pitchstone.
The shores of the Bosporus are composed in the northern portion of different volcanic rocks, such as dolerite, granite and trachyte; but along the remaining course of the channel the prevailing formations are Devonian, consisting of sandstones, marls, quartzose conglomerates, and calcareous deposits of various kinds.
The natural cleavage of the trachyte into joint planes had already scarped out shelves which it was comparatively easy for human labour to shape; and so, high up this cone of trachyte, the Greek town of Assus was built, tier above tier, the summit of the crag being crowned with a Doric temple of Athena.
POROS, or Poro ("the Ford"), an island off the east coast of the Morea, separated at its western extremity by only a narrow channel from the mainland at Troezen, and consisting of a mass of limestone rock and of a mass of trachyte connected by a slight sandy isthmus.
- Recent volcanic eruptive rocks (including rhyolite, trachyte, phonolite, andesite and basalt) have been examined at a number of points throughout both the geological regions of the island.
The volcanic origin of the whole archipelago is proved by the principal rocks being of basalt, trachyte and lava.