Thirdly, the whole substance of the bounding rock suddenly passes into an angulo-concretionary mass of obsidian.
These rocks have an obscure, concretionary structure, and are full of variously coloured angular pseudo fragments.
They all agree in the nodular or concretionary character of the obsidian, and of the passage of these nodules into layers.
Moreover, in the augitic series, there never appears to be any tendency to concretionary action, which we have seen plays an important part in the lamination of rocks, of the trachytic series, or at least in rendering that structure apparent.
It generally affects a nodular orconcretionary structure.
It is composed of phonolite, divided in one part into great curved laminae, in another, into angular concretionary balls, and in a third part into outwardly radiating columns.
The formation, indeed, of a large crystal of any mineral in a rock of mixed composition implies an aggregation of the requisite atoms, allied toconcretionary action.
In an analysis by Vauquelin of a specimen of obsidian from Hecla, which probably flowed as lava, the proportion of silica is nearly the same as in the nodular or concretionary obsidian from Mexico.
They form the passage from the perfectly glassy portions, to those nearly homogeneous and stony, with only an obscure concretionary structure.
Also coarsely and finely granular to perfectly compact, like flint; the compact or cryptocrystalline varieties often assuming botryoidal, stalactitic, and concretionary forms.
And the appearance of a concretionarystructure (pseudo-concretions) is often the result of the concentric decomposition of the rocks by weathering, as explained on page 13.
Rocks often have a concretionarystructure when there are no distinct or separable concretions.
A loose hydrated form of silica, a variety of opal, deposited in concretionary cauliflowerlike masses, around some hot springs and geysers.
Bearing globules; in geology, used of rocks, and denoting a variety of concretionary structure, where the concretions are isolated globules and evenly distributed through the texture of the rock.
Section of spheroidal concretionary Travertin under the Cascade of Tivoli.
A white concretionary limestone, usually hard and semi-crystalline, deposited from the water of springs holding lime in solution.
They are composed of fibrous radiate calcite crystals, which by some kind of concretionary action have segregated from the dolomitic material and grouped themselves together in this way.
The prevalence of crystalline, concretionary and drusy structures in dolomite can thus be simply explained.
Many dolomites, particularly those of the north of England, show a very remarkable concretionary structure.
Defn: A glassy volcanic rock of a grayish color and pearly luster, often having a spherulitic concretionary structure due to the curved cracks produced by contraction in cooling.
Defn: A flattened concretionary nodule, usually of limestone, intersected within by cracks which are often filled with calcite, barite, or other minerals.
Defn: Bearing globules; in geology, used of rocks, and denoting a variety of concretionary structure, where the concretions are isolated globules and evenly distributed through the texture of the rock.
Defn: A loose hydrated form of silica, a variety of opal, deposited in concretionary cauliflowerlike masses, around some hot springs and geysers.
Defn: A white concretionary form of calcium carbonate, usually hard and semicrystalline.
The serpentine and pyroxene which fill the cavities of the calcareous matter have no appearance of concretionary structure.
This, while it shows that these veins have no connection with the fossil, shows also that the latter was an original ingredient of the beds when deposited, and not a product of subsequent concretionary action.
If all specimens of Eozoon were of the acervuline character, the comparison of the chamber-casts with concretionary granules might have some plausibility.
They may, however, be concretionaryin their origin.
The laminæ of carbonate of lime, on the contrary, retain distinct traces of structures which cannot be of a crystalline or concretionary character.
At one place a tuff containing small fragments of basalt displayed a concretionary structure, indicating probably the proximity of a dyke, the globular masses being 4 feet across.
In crossing the range on the way from Lambasa to Ngelemumu, I noticed as high as 450 feet basic non-calcareous tuffs displaying a concretionary arrangement suggestive of the proximity of an intrusive igneous rock.
The finer gravel has a concretionary character, some of the pieces appearing like bits of stick that have been converted into limonite.
They often form the nucleus of concretionary balls of clay-iron-stone, and are well preserved, exhibiting a conical axis, around which a great quantity of scales were compactly imbricated.
Sometimes only concretionary nodules abound in them; but these, where there is an increase in the quantity of calcareous matter, unite into regular beds.
The stratification is very irregular, in some places well-defined, in others obliterated by the concretionary action which has re-arranged the materials of the rocks subsequently to their original deposition.
Cornstone and marl--red and green argillaceous spotted marls, with irregular courses of impure concretionary limestone, provincially called Cornstone.
Several beds of it are frequently seen, either in continuous masses, or in concretionary nodules, one upon another, with layers of marl interposed.
Among the most remarkable examples of concretionary structure are those described by Professor Sedgwick as abounding in the magnesian limestone of the north of England.
It is never crystallized, but may have a fibrous or microcrystalline structure, and commonly occurs in concretionary forms or in compact and earthy masses; sometimes mammillated, botryoidal, reniform or stalactitic.
Granular and concretionary limonite accumulates by organic action on the floor of certain lakes in Sweden, forming the curious "lake ore.
I conceive that this bed, which is only a few feet in thickness, must have assumed its present state through metamorphic and concretionary action.
We should bear in mind what thick strata, in ordinary sedimentary masses, have obviously been formed by a concretionary process.
Some of the beds exhibit a singular concretionary arrangement, with the curves determined by the lines of fissure.
The fragments often blend at their edges into the surrounding granular mass, and seem due to a kind of concretionary action.
The fissures also determine the curvatures of the long undulating zones of concretionary action.
These chemical changes may be the cause of the frequent concretionary structure and veining in the laterite.
In India a calcareous laterite with large concretionary blocks of carbonate of lime is called kankar (kunkar), and has been much used in building bridges, &c.
They usually form a poor soil, full of hard concretionary lumps and very unfertile because the potash and phosphates have been removed in solution, while only alumina, iron and silica are left behind.
The bauxite is earthy, and usually shows a concretionaryor pisolitic structure similar to that observed in residual iron ores (p.
In most of the tertiary clays there are small concretionary nodules, which contain more calcareous matter than the mass of clay around them.
In the coal formation, the nodular iron ore consists of concretionary masses.
The ironstone either occurs in concretionary nodules, often formed around some organic nucleus, or it is an argillaceous ore, having a slaty structure.
It is presumed that the siliceous and calcareous matter was deposited together as sediment, and that the aggregation has resulted from a movement among the particles similar to that by which the concretionary structure is produced.
There are other instances, similar to the last in all respects, except that the segregated portion does not take the concretionary form.
The columnar structure of basalt seems to have resulted from a peculiar molecular action, at first resembling a concretionary arrangement, while the mass was cooling from a state of fusion.
An impacted yellowish-white concretionary matter filled the anterior chamber; and a small quantity of it lay as a fine powder at the bottom of the posterior one.
In the aperture of the anterior blind sac he found a concretionarymatter which he supposed to contain uric acid, but chemical analysis did not confirm the supposition.
A flattened concretionary nodule, usually of limestone, intersected within by cracks which are often filled with calcite, barite, or other minerals.
A white concretionary form of calcium carbonate, usually hard and semicrystalline.
A glassy volcanic rock of a grayish color and pearly luster, often having a spherulitic concretionary structure due to the curved cracks produced by contraction in cooling.
Another very important series of concretionary structures are the flint nodules which occur in chalk, and the patches and bands of chert which are found in limestones.
In deep-sea dredgings concretions of phosphate of lime and manganese dioxide are frequently brought up; this shows that concretionary action operates on the sea floor in muddy sediments, which have only recently been laid down.
Argillaceous sandstones and flagstones very frequently contain "clay galls" orconcretionary lumps richer in clay than the remainder of the rock.
In the red clay of the deep sea bottom concretionary masses rich in manganese dioxide are being formed, and are sometimes brought up by the dredge.
These examples will indicate the great variety of substances which may give rise to concretionary structures.
One must also bear in mind the danger arising from mistaking concretionaryaccumulations of bituminous matter for sporangia.
They sometimes form the nucleus of nodular, concretionary balls of clay-ironstone, and are well preserved, having a conical axis, surrounded by scales compactly imbricated.
The presence in the old Peruvian guano of concretionary nodules has already been referred to.
Chincha guano--little round concretionary nodules, varying in colour from pure white to dark brown, were occasionally found.
Fine grassy forest-land intervened between the Bricklow and Myal scrubs; the latter is always more open than the former, and the soil is of a rich black concretionary character.
In many rocks a concretionary structure may be observed.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "concretionary" in a variety of sentences. We hope that you will now be able to make sentences using this word.
