The dark-green schists in this neighbourhood are partly much weathered, partly hard and untouched.
It becomes narrower and narrower, till at length there is a passage only five yards broad between walls of schists tilted up vertically.
Green schists form small ledges and strips on the otherwise soft ground, so that at a distance the land seems striped with black.
The name given by Sir Roderick Murchison to a vast series of fossiliferous strata, which lies between the non-fossiliferous slaty schists below and the old red sandstone above.
The schists are more especially to be found in the heart of mountain-chains, and in regions where the lowest and oldest parts of the earth's crust have, in the course of geological revolutions, been exposed to the light of day.
Rocks which present this aspect are known as schists (q.
It is not proposed at present to undertake the study of the crystalline schists of the Rocky Mountain region.
Raphael Pumpelly, assisted by a corps of geologists, and the field of his work is the crystalline schists of the Appalachian region, or eastern portion of the United States, extending from northern New England to Georgia.
He will also include in his studies certain paleozoic formations which are immediately connected with the crystalline schists and involved in their orographic structure.
Fossil-bearing Carboniferous overlies them but no other indication of their age was obtained save their general position in the belt of schists already mentioned.
At distant points the schists assume a darker hue and take on the characters of a rather typical mica schist.
The deeply weathered fissile mica schists east of Pasaje (see Appendix C for all locations) are also unconformably overlain by conglomerate and sandstone of Carboniferous age.
The Cordillera Vilcapampa has an axis of granitic rock which was thrust upward through schists that now border it on the west and slates that now border it on the east.
From the fact that their disturbance has been on broad lines over wide areas with extreme metamorphism, they are to be separated from the older mica-schists and the crumpled chlorite schists of Puquiura and Pasaje.
It will be seen that we have here more than a mere crinkling, such as the mica schistsof the Cordillera Vilcapampa display.
The Silurian is from a Bolivian locality south of La Paz but in the great belt of shales, slates, and schists which forms one of the oldest sedimentary series in the Eastern Andes of Peru as well as Bolivia.
It consists of (1) a great mass of slates and shales with remarkable uniformity of composition and structure over great areas, and (2) older schists and siliceous members in restricted belts.
At Pasaje, on the western side of the Apurimac, the Carboniferous again appears resting upon the oldschists described on p.
It is the centre of a district very rich in minerals, obtained from a narrow stretch of crystalline schists underlying the Tertiary deposits.
Crystalline schists occupy a large part of the country, forming all the higher mountain ranges.
In the eastern part of the island the predominant rocks are schists of unknown age, with intrusive masses of serpentine and euphotide.
Folded amongst the schists are Strips of Upper Carboniferous beds similar to those of the west coast.
I found much of it at several "horizons" of the slope back of French Hill, and also as a cap overlying the badly cleaved and fragmented schists of the summit (three thousand feet?
In its more distinctively geological relations the Klondike region may be broadly defined as one composed in the main of schists and schistose rocks, defining an area of considerable disturbance.
The trachyte of the Drachenfels was probably the neck of a volcano which burst through the fundamentalschists of the Devonian period.
They are succeeded unconformably by Eocene deposits, consisting of sandstones with coal-seams and limestones containing Nummulites, Alveolina and Orthophragmina; and these beds are as limited in extent as the Cretaceous schists themselves.
The Cretaceous schists have yielded fossils only at Banjarnegara, where a limestone with Orbitolina is interstratified with them.
The alum of European commerce is fabricated artificially, either from the alum schists or stones, or from clay.
The schists contain only the elements of two of the constituents, namely, clay and sulphur, which are convertible into sulphate of alumina, and this may be then made into alum by adding the alkaline ingredient.
The manufacture of alum from alum schists may be distributed under the six following heads:--1.
The brown coal schists contain, commonly, some green vitriol crystals spontaneously formed in them.
It is however among the oldest talc-schists and clay slates, that it usually occurs.
Those bituminous alum schists which have been used as fuel under steam boilers have suffered such a violent combustion that their ashes yield almost no alum.
Beds of granular limestone, or of calcareous schists are also never altogether wanting; while iron pyrites and graphite, in lenticular masses, or in local beds conformable to the great mass of the gneiss strata, are very generally present.
Such as the seeming intercalation of crystalline schistswith fossiliferous rocks, or the immediate sequence of the two.
Though the Secondary rocks of the Alps have undergone, in places, some modification and mineral changes, these are very different from the metamorphism of those crystalline schists which have a stratified origin.
The apparent superposition of crystalline schists to rocks with fossils is due to over-folding or over-thrust faulting--i.
Towards the middle of April he proceeded northward, in order to examine the perplexing schists and less altered sedimentary deposits of the Taconic range, rocks which from that time to this have given ample employment to geologists.
The schists can be definitely called volcanic in many cases, from macroscopic characters, such as the component minerals and basaltic arrangement.
Additional minerals found in the coarse schists are calcite, ilmenite, skeleton oblivine, biotite, and hematite.
This final stage is macroscopically nothing more than a siliceous slate or schist, and is barely distinguishable from the end products of similar metamorphism in the more feldspathic schists and the Loudoun sandy slates.
Deposits of copper in the schists have long excited interest and led to mining operations.
Ancient schists occur on the east coast south of Angmagssalik, and basalts and schists are found in Scoresby Fjord.
By increasing metamorphism greywackes frequently pass into mica-schists, chloride schistsand sedimentary gneisses.
The schists and gneisses of the Ox Mountain axis also enter the county north of Castlebar.
The beds consist of selenitic and calcareous schists and beds of clay, mixed with numerous beds of pyrites.
At the early periods in which the materials of the ancient crystalline schists were accumulated, it cannot be doubted that the chemical processes which generated silicates were much more active than in more recent times.
Mica-schists occur extensively in Brittany, in the Vosges, in the Pyrenees.
Limestones, sandstones, and schists (slates of Angers) form the chief part of this series.
At first they consist of mica-schists and bits of porphyry, but blocks of syenite soon become intermingled.
The clear coast sections of Eriboll have now taught me that the parallelism between the Silurian strata and the overlying schists is not due to conformable deposition.
Finally, the copper schists containing bitumen or sulphur are roasted, and then smelted with stones which easily fuse in a fire of the second order, and are made into cakes, on the top of which the slags float.
The schists exude it more plentifully than the pyrites.
On the Norwegian side the Cambrian is perhaps represented by the Roros schists which lie at the base of a great series of crystalline schists, the probable equivalent of Ordovician and Silurian rocks.
The oldest rocks, forming the greater mass of the hinterland, are gneisses, schists and granites of Archaean age.
Iona is composed entirely of ancient gneisses and schists of Lewisian age; these include bands of quartzite, slate, marble and serpentine.
Almost the entire area of this county is occupied by the younger Highland schists and metamorphic rocks.
On the north the schists come first, sometimes rising into peaks and ridges in a state of ruin .
Illustration] The geological sequence begins with the granite and schistsof the central zone, which form a band extending from Fisht on the west to a point some distance beyond Kasbek on the east.
Above that the crystalline schists are bare of tree vegetation.
Important deposits may be expected at or about the line of unconformability where slates, shales, quartzites, sandstones, limestones, schists and other sedimentary deposits are pierced by intrusive masses of igneous rocks.
The junction of slates and schists with igneous or metamorphic rocks often proves a valuable find of mineral.
On the other hand, when compact limestones or ancient schists formed the foundation-rock, the amount of damage was conspicuously less than in other cases.
They are formed chiefly of crystalline gneissic and granitic rocks and some metamorphic schists and quarzite, with cretaceous and tertiary rocks of varying thickness along its southern edge.
In the collections made by Watson and Hoadley at the Western Base (Queen Mary Land) gneisses and schists were ascertained to be the predominant types.
There were about eighty acres of rock exposed on the edge of the ice-cap, mainly composed of mica schists and some granite; the whole extensively weathered.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "schists" in a variety of sentences. We hope that you will now be able to make sentences using this word.
