The zones in the columnar trachyte are generally contorted; they extend uninterruptedly for a great length in a vertical direction, and apparently parallel to the walls of the dike-like mass.
The jasper is of an ochre yellow or red colour; it occurs in large irregular masses, and sometimes in veins, both in the altered trachyte and in an associated mass of scoriaceous basalt.
The central parts of this island consist of irregularly rounded mountains of no great elevation, composed of trachyte, which closely resembles in general character the trachyte of Ascension, presently to be described.
Mr. Scrope gives as an illustration of this structure a resinous trachyte or pitchstone-porphyry in one of the Ponza islands, which rise from the Mediterranean, off the coast of Terracina and Gaeta.
In Auvergne, the Eifel, and other countries where trachyte and basalt are both present, the trachytic rocks are for the most part older than the basaltic.
The name trachyte (from trachus, rough) was originally given to a coarse granular feldspathic rock which was rough and gritty to the touch.
Granite and mica slate are shaken as well as limestone and sandstone, or as trachyte and amygdaloid.
Some groups of dolerite andtrachyte indicate p 258 a certain degree of basaltic fluidity; others, which have been expanded into vast craterless domes, appear to have been only in a softened condition at the time of their elevation.
In the waning light of evening the polygonous pyramid of dark trachyte appears as a powerful vision of the mystery of existence shining through a veil of translucent gold.
Such rocks as basalt, diorite and trachyte are comparatively rare.
The overlying rocks, which seem to have been poured from the centre of this tract, consist of masses of trachyte and columnar basalt, of pyramids of wacke, and beds of lava and tufwacke, with strata of conglomerates and sandstones.
A long march brought us the same day to the river Alelta, a tributary to the Nile, and forming near the encampment Lake Sertie, a full mile in diameter, bounded by low hills of trachyte and porphyry.
The trachyte is generally a compact mass of grey feldstein, which contains crystals of glassy feldspar, irregularly embedded, and in different quantities.
The auriferous ores of Hungary and Transylvania, composed of tellurium, silver pyrites or sulphuret of silver, and native gold, lie in masses or powerful veins in a rock of trachyte or in a decomposed felspar subordinate to it.
From this gorge you suddenly come upon the town, situated in an amphitheatre of grand gray, trachyte rocks.
In texture and general aspect rhyolite and trachyte are nearly identical.
Obsidian is, in fact, simply rhyolite or trachyte which, cooling quickly, has not had time to crystallize, but has remained permanently in the amorphous or glassy state.
Tachylite is a highly basic volcanic glass, standing in the same relation to basalt and andesite that obsidian does to trachyte and rhyolite.
Not a single specimen of its trachyte has ever been deposited in a European museum.
From this very sharp peak, I brought away thin plates of trachyte perforated by lightning, and within the holes of a melted glassy surface, resembling those brought from Little Ararat.
Trachyte and basalt, with dykes like Cyclopean walls, are cut to jagged needles by the furious north-easter.
A gutter leads from the mouth, showing signs of water-wear, and the blocks of trachyte are so loaded with glossy white felspar that I attempted to dust them before sitting down.
The existence even of trachyte has not yet been verified in the Sierra Nevada de Merida which links the Andes and the littoral chain of Venezuela.
This trachyte is greyish white in colour and easily workable, but hardens by exposure.
Next to these was a clock frame made out of trachyte in the form of a Greek temple.
These latter strata are perhaps related to a mass of columnar trachyte which occurs behind Castro.
Winding through the porphyry, in a serpentine course, there is also a stream of obsidian, as it is called here, or volcanic glass, mixed with trachyte and quartz bowlders.
I cannot redescribe the way in which these bristling peaks of purple and green trachyte cut the tremulous sky, nor try to make you understand anew the abysses that sink narrowly between the closely crowded mountains.
The trachyte is of itself yellowish white; when it is stained with the black oxide of manganese and the red oxide of iron that variegates the ores, it is sure to carry silver, though this (in the form of a chloride) can rarely be seen.
When the trachyte was poured out this granite apparently formed a ridge which rose above the level of the fluid mass of the surrounding volcanic rock, and therefore was not covered by it.
The last of the trachyte peaks are at the head of Mosquito pass.
The former is supposed to be a true fissure vein in the trachyte rock, the cavity of which, after the rocks were rent asunder, was filled with well rounded pebbles and bowlders, generally similar in constitution to the country rock.
The ores abound in a thousand ledges which run up and down, and here and there, all through the mountains, from the metamorphic limestones of the outer ledges to the storm-hewn trachyte that caps the hoary summits.
Extending into the trachyte formation from the southwest, and following its general direction, is a tongue-shaped mass of granite about three-fourths of a mile wide and at least seven or eight miles long.
The weight of these monoliths is calculated at five or six tons, and they were cut from quarries in the trachyte rock of the mountains some five miles away, and more than 1,000 feet above the site of Mitla.
As has been shown, the beautiful trachyte of Mitla, which, whilst it is tough and enduring, is soft, and lends itself readily to the chisel.
Indeed, the nature of the building has doubtless obeyed the character of the stone, which does not lend itself to careful cutting and carving like the easily-worked trachyte of Mitla.
Round about the crater of the Rana-Raraku volcano, forty of these figures have been counted, all of a similar type, all cut in one piece of solid trachyte rock.
Its shores are paved with masses of trachyte and obsidian.
Passing northward through dense woods and almost impenetrable fire-slashes, the next noteworthy region arrived at is the valley of Bridge Creek, the creek receiving its name from a natural bridge of trachyte thrown across the stream.
The trachyte may sometimes be concealed by the conglomerates, but I am inclined to think that each one has formed a centre of effusion.
The forest grows close down to the margin of the river, making travel very difficult, and in one place the hills of trachyte almost close in the valley.
At a height of 300 feet a light grey highly altered oligoclase-trachyte (sp.
It is, however, a highly altered oligoclase-trachyte (sp.
It looks like a limestone and effervesces freely with an acid; but it is in fact a highly altered oligoclase-trachyte (sp.
The two rocky points on the north coast opposite the hill are formed in one case of a somewhat altered oligoclase-trachyte and in the other of a quartz-porphyry.
It is an oligoclase-trachyte impregnated with crystalline silica and exhibiting a singular prismatic structure, the small columns or prisms being only 3 or 4 inches in diameter.
Decomposing altered white acid tuffs here occur with occasional large blocks, a couple of tons in weight, of apparently a quartz-porphyry or trachyte with its structure disguised by silicification.
The trachyte is ordinarily reddish, greyish, or blackish; it mostly contains mica.
In the Lower Eifel, eruptions of trachytic lava preceded the emission of currents of basalt, and immense quantities of pumice were thrown out wherever trachyte issued.
It has been remarked that in Auvergne, the Eifel, and other countries where trachyte and basalt are both present, the trachytic rocks are for the most part older than the basaltic.
As both trachyte and basalt pass into clinkstone, the rock so called must be very various in composition.
Some varieties of trachyte contain crystals of quartz.
The hills are composed of loose scoriae, blocks of lava, lapilli, and pozzuolana, with fragments of trachyte and granite.
Pumice occurs in great quantity; and there are conglomerates, or rather breccias, wherein fragments of trachyte are bound together by pumiceous tuff, or sometimes by silex.
A striking example of this structure occurs in a resinous trachyte or pitchstone-porphyry in one of the Ponza islands, which rise from the Mediterranean, off the coast of Terracina and Gaeta.
But we see no reason why they could not be the upper portion of the solidtrachyte cone blown into the air at the great eruption which cleared out this enormous crater.
The prevalence of trachyte shows that the products have cooled under feeble pressure.
Pumice and trachyte are the most common rocks around this mountain, and these are augitic or porphyroid.
The Ecuadorian volcanoes have rarely ejected liquid lava, but chiefly water, mud, ashes, and fragments of trachyte and porphyry.
The characteristic rock is a black vitreous trachyte resembling pitchstone, but anhydrous.
The trachyte which once formed the summit of this mountain is now spread in fragments over the plain of Riobamba.
Footnote 60: "As a general rule, whenever the mass of mountains rises much above the limit of perpetual snow, the primitive rocks disappear, and the summits are trachyte or trappean porphyry.
The mountain chain is built up of granite, gneissoid, and schistose rocks, often in vertical position, and capped with trachyte and porphyry.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "trachyte" in a variety of sentences. We hope that you will now be able to make sentences using this word.
