Both augite-andesite and hypersthene-andesite occur, while at the southern end of this interglacial rock mass, just east of Cowlitz Glacier, the cliffs are composed of the prismatic black basalt.
In one andesite the abundance of these remnants of hornblende and also of augite anhedrons in the groundmass may justify the conclusion that this augite andesite is of derivative origin, of the class described by Washington.
The granite, however, exhibits no intrusive characters, while the overlying andesite becomes scoriaceous in its lower portion, although compact immediately above.
In petrographic character the lavas range from hypersthene-andesite to basalt.
A black, loose-textured andesite is most abundant, and from its occurrence on the edge of this well-defined crater may be regarded as representing the later eruptions of Rainier.
Blocks of andesite cover the slope, deposited there by the glacier at a time when it possessed greater lateral extent, and the granite talus from above crosses this same slope in a narrow band.
Above this ridge of granite on the one side tower the cliffs of bedded volcanics which compose the Sluiskin Mountains, and on the other is the andesite ridge bounding the canyon of Winthrop Glacier.
The distribution of these types indicates a radial arrangement of lava streams, and hypersthene-andesite is the more abundant variety of lava.
In the same flow hypersthene-andesite may occur in one portion, while in close proximity the lava is an augite-andesite.
Hornblende is not abundant in any of the rocks studied, although typical hornblende-andesite has been described among the specimens collected by Professor Zittel.
On Crater Peak, and below on Gibraltar, hypersthene andesite occurs with considerable variation of color and texture.
Tachylite is a highly basic volcanic glass, standing in the same relation to basalt and andesite that obsidian does to trachyte and rhyolite.
It is a comparatively rare rock, for the reason that basalt and andesite crystallize more readily than the acidic rocks on passing from the liquid to the solid state.
To my surprise, I found a twelve-foot vein of free-milling ore, on a contact between andesite and Silurian limestone.
Propylitization consists in the replacement of the original minerals of the andesite by secondary products such as kaolin, epidote, mica, chlorite, quartz and chalcedony, often with the retention of the igneous structures of the rocks.
It occurs, for example, in theandesite of the Andes, from whence it derives its name.
The strata consist mainly of conglomerates and sandstones, which, at Gartly and at Rhyme, are associated with lenticular bands of andesite indicating contemporaneous volcanic action.
The prevailing colour of the stones is a bleached yellow verging upon a delicate pink; but these paler strata are divided by veins of bluish andesite pointing upwards, like spear-heads, from the base (Fig.
Skirting the buttresses of the eastern wall, we observed that they were composed of a compact grey andesite with something of the appearance of slate.
In the United States sapphires are recovered from alluvial deposits along the Missouri River near Helena, Montana, where they are supposed to have been derived from dikes of andesite rocks.
A later series of small diorite or andesite dikes cut the ore bodies.
The tunnel, cut through hardandesite rock, under a ridge fifteen hundred feet higher, is nearly three miles long, and the passage through it takes ten minutes.
The Andesite group forms a connecting link between the highly acid and the basic groups, and there are many varieties of the above which it is not necessary to enumerate.
Such metamorphosed areas are generally accompanied by numerous dikes and injected masses of andesite and various porphyries: I have in several places traced the metalliferous veins from the intrusive masses into the encasing strata.
Beyond the junction of the Yeso and Volcan, the porphyritic strata appear to dip towards the hillocks of andesite at an angle of 40 degrees; but at some distant points on the same ridge they are bent up and vertical.
Illapel), likewise, there are numerous veins of copper- pyrites and of gold, both in the strata of the gypseous formation and in the injected hills of andesite and various porphyries.
Claro, which is interesting from containing fossils: the strata are much dislocated by faults and dikes, and are inclined to the north, towards a mountain of andesite and porphyry, into which they appear to become almost blended.
We have seen that andesite occurs in three places in Tierra del Fuego; in Chile, from S.
The type of acid andesite which is displayed in the upper two-thirds of the hill is distinguished from those of the other hills of the Ndrandramea district by its orthophyric groundmass.
The tuffs composing the cliffs are horizontally bedded and overlie the prevailing aphanitic augite-andesite exposed on the valley-slopes below.
Displayed in mass in the bed of the river in the same locality, and beneath the submarine tuff just referred to, is a porphyritic basaltic andesite (sp.
It contains pebbles and blocks of acid and basic andesitic rocks, and may be described as an altered hornblende-andesite tuff.
I found the same grey andesite exposed in situ lower down the south slope at an elevation of 1,800 feet, but non-scoriaceous.
The rocks in question are tuff-agglomerates, the small blocks of pyroxene-andesite standing out from the tuff having a polaric force of 14° or 15°.
The hornblende-andesite of Na Raro, as in the case of the rocks of most of the other peaks of acid andesites, has its peculiar characters.
Above the basic tuffs lie a series of tuffs, about 5 feet in thickness, and composed mainly of the debris of acid andesitic rocks of the hornblende-andesite type, such as occur in the Ndrandramea district.
In a stream at the foot of the east slope occur small blocks of basaltic andesite probably derived from a dyke.
Lindgren says: "By far the greater part of the andesite occurs in the form of a tuffaceous breccia in numerous superimposed flows.
Over large areas in the Truckee quadrangle the andesite masses consist of breccias containing numerous dykes and necks of massive andesite.
To the left are great andesite crowns on the mountain tops.
The andesite masses here in places attain a thickness of 2000 feet.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "andesite" in a variety of sentences. We hope that you will now be able to make sentences using this word.
