Slates sentence example
This boss is bounded, except on the south, by the Witwatersrand series, the lower portion of which consists of quartzites and slates and the upper portion of quartzites and conglomerates.
The western portion of Kotelnyi is built up of Middle Devonian limestones and slates, folded the same way, of which the fossil fauna is similar to that of the Urals.
Triassic slates appear in the south-east.
The baptismal fonts date from the 12th century, and the curious spire in the form of an elongated pumpkin and covered with slates gives a fantastic and original appearance to the whole edifice.
They are rarely metamorphosed to the point of recrystallization, though locally shales are altered to roofing slates, sandstones are indurated, limestones slightly marblized, and coals, originally bituminous, are changed to anthracite in northern Pennsylvania, and to graphite in Rhode Island.Advertisement
Upon the folded slates and schists which constitute these inliers the Devonian rests with marked unconformity; but north of the ridge of Condroz Ordovician and Silurian beds make their appearance.
Slates properly so-called do not, except on rare occasions, split along the bedding, but along planes of cleavage, which intersect the bedding usually at high angles.
The original material was a fine clay, sometimes with more or less of sand or ashy ingredients, occasionally with some lime; and the bedding may be indicated by alternating bands of different lithological character, crossing the cleavage faces of the slates, and often interrupting the cleavage, or rendering it imperfect.
Slates belong mostly to the older geological systems, being commonest in Pre-Cambrian, Cambrian and Silurian districts, though they may be found of Carboniferous or even of Tertiary age, where mountain-building processes have folded and compressed these more recent formations.
The action of pressure is shown also by the fossils which sometimes occur in slates; they have been drawn out and distorted in such a way as to prove that the rock has undergone deformation and has behaved like a plastic mass.Advertisement
If the bedding be traced, either in the slates or in the other rocks which accompany them, flexures will be frequently observed (the folding often being of an isoclinal type), while reversed faulting, or thrusting, is usually also conspicuous.
This structure is by no means confined to slates, though always best exemplified in them, owing probably to the finegrained, argillaceous materials of which they consist.
The cleavage of slates must be distinguished from cleavage of minerals, the latter being due to different degrees of cohesion along definite crystallographic planes.
This method of reasoning, however, does not carry us far, as the minerals of slates vary considerably in form.
Pressure will also tend to produce an expansion of the rock mass in a direction (usually nearly vertical) at right angles to the compression, for such rocks as slates are distinctly plastic in great masses.Advertisement
Slates consist largely of thin plates of mica arranged parallel to the cleavage faces.
Micas and other platy minerals (such as chlorite), which naturally grow most rapidly on their edges, would show this tendency best, and such minerals usually form a large part of the best slates; but even Sketch (by Du Noyer) of a block of variegated slate from Devil's Glen, Co.
A structure akin to cleavage, often exemplified by slates especially when they have been somewhat contorted or gnarled, is the Ausweichungsclivage of Albert Heim.
The faces of slates have usually a slightly silky lustre due to the abundance of minute scales of mica all lying parallel and reflecting light simultaneously from their pearly basal planes.
In microscopic section the best slates show much colourless mica in small, thin, irregular scales.Advertisement
Minute rods or needles of rutile are also common in slates, and well-formed cubes of pyrites are often visible on the splitting faces.
The brownish colour of some slates is due to limonite and haematite, but magnetite occurs in the darker coloured varieties.
By advancing crystallization and increased size of their components, slates pass gradually into phyllites, which consist also of quartz, muscovite and chlorite.
In the neighbourhood of intrusive granites and similar plutonic igneous rocks, slates undergo "contact alteration," and great changes ensue in their appearance, structure and mineral composition.
Farther away from the granite the slates are not so much altered, but generally show small rounded or ovoid spots, which may be darker or lighter in colour than the matrix.Advertisement
In these spotted slates andalusite, chiastolite, garnet and cordierite often occur; chiastolite is especially characteristic; cordierite occurs only where the alteration is intense.
In other cases, especially near mineral veins, slates are filled with black needles of tourmaline or are bleached to pale grey and white colours, or are silicified and impregnated with mineral ores.
Frequently in districts where slates are much crumpled they are traversed by numerous quartz veins, which have a thickness varying from several inches up to many feet, and may occasionally be auriferous.
The finer varieties are made into writing slates, and in districts where cross cleavage exists slate pencils are made.
From the mass thrown out by the blast, or loosened so as readily to come away by the use of crowbars, the men select and sort all good blocks and send them in waggons to the slate huts to be split and dressed into slates.
These plates are then placed horizontally by the dresser on a vertical iron "stand," and cut with a sharp knife into slates of various sizes suitable for the market.
For an enumeration of these sizes, see Roofs, where also will be found an account of the different varieties of slates and of the ways in which they are fixed.
There are ancient rocks, however, in New Caledonia, which .has a geological affinity with New Zealand; old sedimentary rocks are known in New Pomerania, besides granite and porphyry, and slates, sandstone and chalk occur in Fiji, as well as young volcanic rocks.
Ironstone and roofing slates are quarried, and there is some industry in agatepolishing and the manufacture of trinkets.
The carbon-bearing shales, slates and schists, and the limestone, are indications that life was relatively abundant, even though but few fossils are preserved.
A series of quartzites and slates referred to the Cambrian, and holding numerous and important veins of auriferous quartz, characterize its Atlantic or southeastern side, while valuable coal-fields occur in Cape Breton and on parts of its shores on the Gulf of St Lawrence.
Llanidloes has a trade in Plinlimmon slates and minerals besides flannel and wool manufactures.
The chief imports are Baltic timber, coal, salt and manure; and the exports, manufactured goods, grain, potatoes and slates.
It is formed chiefly of slates, grits and porphyries of the Cambrian and Silurian systems. It consists of five "ribs" converging at the summit, 3560 ft.
They may be supported by iron standards or brick piers, back and front, bearing up a flat bar of iron on which the slates may rest; the use of the bar will give wider intervals between the supports, which will be found convenient for filling and emptying the beds.
They are generally of lenticular form, and usually occur in or near the contact of eruptive rocks with schists or slates; the presence of the igneous rock being probably connected genetically with their origin.
The mineral products of the district also include lignite, copper, manganese, vitriol, lime, gypsum, volcanic stones (used for millstones) and slates.
These rocks are much folded and the shales are locally cleaved into slates, while the sandstones and conglomerates form scarps and ridges.
Carboniferous beds, consisting chiefly of slates, sandstones and conglomerates, are found in the south-eastern provinces.
The geology of Borneo is very imperfectly known The mountain range which lies between Sarawak and the Dutch possessions, and may be looked upon as the backbone of the island, consists chiefly of crystalline schists, together with slates, sandstones and limestones.
Murchison published his Silurian system in 1839, wherein he recognized the Cambrian to include the barren slates and grits of Harlech, Llanberis and the Long Mynd.
Thus, we find them more frequently, folded, tilted and cleaved; the muds have become shales, slates, phyllites or schists, the grey and red sands and conglomerates have become quartzites and greywackes, while the limestones are very generally dolomitized.
Certain markings on slates and sandstones, such as the "fucoids" of Scandinavia and Scotland, the Phycoides of the Fichtelgebirge, Eophyton and other seaweed-like impressions, may indeed be the casts of fucoid plants; but it is by no means sure that many of them are not mere inorganic imitative markings or the tracks or casts of worms. Oldhamia, a delicate branching body, abundant in the Cambrian of the south-east of Ireland, is probably a calcareous alga, but its precise nature has not been satisfactorily determined.
The Cambrian rocks of Ireland, a great series of purple and green shales, slates and grits with beds of quartzite, have not yet yielded sufficient fossil evidence to permit of a correlation with the Welsh rocks, and possibly some parts of the series may be transferred in the future to the overlying Ordovician.
While the general elevation is 7000 to 9000 ft., the individual peaks, consisting largely of granites and metamorphic slates, reach altitudes of 10,000 ft.
The southern parts of the central range are composed of granites, syenites, porphyries and crystalline slates, while in the north of Ichinskaya volcano, which is the highest summit of the peninsula (16,920 ft.), the mountains consist chiefly of Tertiary sandstones and old volcanic rocks.
The Russian Altai is composed mainly of mica and chlorite schists and slates, together with beds of limestone, and in the higher horizons Devonian and Carboniferous fossils occur in many places.
The rocks consist of sandstones, quartzites, slates and shales, associated with lenticular masses of limestone.
The slates of the Silurian have been bent into folds, and saddle reefs occur along the axis of the folds, as at Hargraves.
Granites and granodiorites were intruded at this period into the older rocks, and altered the adjacent Devonian beds into slates and quartzites, and formed gold-quartz veins, which have been worked in the Devonian rocks at Yalwal.
The hills of the north-western shore afford a variety of granites and crystalline slates of the Laurentian system, whilst Valamo island is made up of a rock which Russian geologists describe as orthoclastic hypersthenite.
But on the south side the crystalline rocks are succeeded by a broad belt of slates, as to the age of which the evidence is at present conflicting and the opinion of geologists divided.
East of Adai-khokh, by what seems a strange freak of nature, the granitic [main] range is rent over and over again to its base by gorges, the watershed being transferred to the parallel chain of clay slates.
These basins or ` longitudinal folds ' are enclosed on the south by the long high ridge of dark slates, which extends parallel to the crystalline [main] chain from the neighbourhood of Sukhum-Kale to the Krestovaya Gora [pass of Darial.] Behind this slate crest spreads a confused multitude of hills, Jurassic and Cretaceous in their formation..
Then follow the Palaeozoic schists and slates.
These are overlaid by sandstones, slates and limestones, alternating with porphyries and porphyrites, sometimes in the form of sheets, sometimes as breccias and conglomerates.
The most prominent member of the Cango series is a coarse conglomerate; the other rocks include slates, limestone and porphyroids.
Among the sedimentary rocks we have, for example, in the clay slates of the Silurian formations, rocks no less cracked and fissured than others, but generally quite impermeable by reason of the joints being packed with the very fine clay resulting from the rubbing of slate upon slate in the earth movements to which the cracks are due.
Slates, schists, quartzites and limestones form the greater part of the hills, but the Brocken and Victorshohe are masses of intrusive granite, and diabases and diabase tuffs are interstratified with the sedimentary deposits.
The quarries have been worked since 1630 and yield some eight million slates every year.
Like the highlands of eastern Asia, those of Turkestan are mostly built up on Pre-Cambrian gneisses and metamorphic slates, resting upon granites, syenites, old orthoclase porphyries, and the like.
On either flank the Silurian shales, slates and sandstones, which are very rarely fossiliferous, rise with steep dips.
In southeastern Wexford, in northern Wicklow (from Ashford to Bray), and in the promontory of Howth on Dublin Bay, an apparently earlier series of green and red slates and quartzites forms an important feature.
Towards the south-east, slates, quartzites and iron-bearing schists occur, but their age is not known.
The Ordovician system has not been certainly identified; but probably many of the slates and quartzites.
The rocks are best known by the limestones in the lead mining field at Zeehan, and the slates, including the tin mine of Mount Bischoff.
The laminated structure of shales, though partly due to successive very thin sheets of deposit, is certainly dependent also on the vertical pressure exerted by masses of superincumbent rock; it indicates a transition to the fissile character of clay slates.
These are overlaid by conglomerates, limestones and clay slates of very doubtful age, the most interesting being a radiolarian clay which occurs on the south side of the Matinang Mountains, at the north end of Lake Posso, &c.; it may correspond with the radiolarian cherts of Borneo.
In the Middle Devonian deeper water conditions have produced mudstones, thin limestones and slates which rarely yield fossils.
The shape is actually hexagonal to avoid three layers where adjacent slates and courses meet.
Fiber cement slate But, I hear you say, what about fiber cement slates and resin slates that are not laminar stone?
Double lap slates have no nibs, relying on the nails or hooks for their fixing.
Andrew Newton Slates are not porous, at least not in the sense you mean.
Dedicated to supplying only proven quality slates, all SSQ products are tested to meet a range of international standards.
Some roofers have been known to once nail and tail rivet some slates on a roof.
Rivets The copper tail rivets The copper tail rivet located in the tail of a standard slate is normally located in the joint between the two lower slates.
If you can see daylight between the slates then there has been slippage and you need a professional roofer to fix it.
This reversible section may be used either with interlocking slates, or natural and man-made double lap slates.
The idea of identical babies with blank slates for minds had been under attack for some time.
I'm running out of clean slates to give her.
Iron goods of various kinds, glass and pottery, school slates, pencils and marbles are produced; the abundant timber fosters the manufacture of all kinds of wooden articles, especially toys; and the textile industry and the manufacture of leather goods, papier mache and sewing-machines are also carried on.
On the eastern side of the range, after a steep descent, the granite formation speedily gives place to slates of vast depth, intersected here and there by fissures of quartz containing gold, and in many places covered by limestone which has been superimposed upon the slates.
Between the "Cotton Belt" and the Tennessee Valley is the mineral region, the "Old Land" area - "a region of resistant rocks" - whose soils, also derived from weathering in situ, are of varied fertility, the best coming from the granites, sandstones and limestones, the poorest from the gneisses, schists and slates.
In the Ardennes the system is represented by grits and sandstones, shales, slates and quartz schists, and includes also whet slates and some igneous rocks.
When completely re-covering a roof, the maximum number of old slates should be re-used.
In 1980, the roof was re-covered with slates.
Rivets The copper tail rivet located in the tail of a standard slate is normally located in the joint between the two lower slates.
Eight oak pillars support a roof tiled with stone slates.
A piece of slate yields roofing slates at the rate of four to just over the inch.
I 'm running out of clean slates to give her.
Resin slates not made in a press can often be more variable than clay tiles due to the wet nature of the process.
Besides its well-known Levi's brand products, the company also markets clothing and accessories under the brand names Dockers, Britannia, and Slates.
Instead of the old styled glass umbrella table, newer materials like plastic laminates, all-weather wickers, resins, tiles and slates are popular for modern lawn furniture.
Bricks, blocks, decorative stones, slates and just plain old rocks picked up from your property can be arranged to form raised garden beds.
Babies were once thought to enter the world with minds that were blank slates that developed through a lifetime of experiences.
They consist of a series of unfossiliferous crystalline slates.
The Cambrian is represented by blue clays, ungulite sandstones and bituminous slates in Esthonia and St Petersburg.
In the centre of the folds fossiliferous beds with crinoids have been found, and the black slates at the top of the series contain Myophoria and other fossils, indicating that the rocks are of Triassic age.
Schists in the common acceptance of that term are really highly crystalline rocks; fissile slates, shales or sandstones, in which the original sedimentary structures are little modified by recrystallization, are not included in this group by English petrologists, though the French schistes and the German Schiefer are used to designate also rocks of these types.
The development of foliation in shaly rocks is undoubtedly closely akin to the production of cleavage in slates.
The phyllites (q.v.) form a middle term between this group and the slates; they consist usually of quartz, white mica and chlorite, and have much of the foliation and schistosity of the mica-schists.
Abich (Sur la structure et la geologic du Daghestan, 1862), the successive folds of Jurassic limestones and slates, all nearly parallel to the Caucasus, which form lofty, narrow plateaus.
The southern part of Mainland, from Laxfirth Voe to Fitful Head a series of dark schists and slates, is found with subordinate limestones.
The principal imports are coal, timber and slates, and the principal export stone of the Transition limestone or Devonshire marble.
Walchi is abundant in the Oolitic lithographic slates of Bavaria.
They show a great variety of type made up of slates, quartzites, occasional conglomerates, schists with large masses of intrusive granites and gneiss.
The lower group (Hospital Hill slates) consists of quartzites and shales, resting on the eroded surface of the older granites and schists, and estimated to be from 10,000 to 12,000 ft.
The Black Reef Series is composed of quartzites, sandstone, slates and conglomerate.
In the Marico district the shales become highly ferruginous and resemble the Hospital Hill slates of the Witwatersrand series.
Most of the island is occupied by the band of the old rocks, which include mica, glaucophane and sericite-schists and slates; there are small intrusions of granite, and numerous dikes and masses of basic eruptive rocks.
The Eastern Andes is a magnificent range in the southern part of Peru, of Silurian formation, with talcose and clay slates, many quartz veins and eruptions of granitic rocks.
Overlying these amongst the Palaeozoic rocks, we meet in many parts of Japan with slates and other rocks possibly of Cambrian or Silurian age.
There is also amongst the Palaeozoic group an interesting series of red slates containing Radiolaria.
Mesozoic rocks are represented by slates containing Ammoniles and Monotis, evidently of Triassic age, rocks containing Ammonites Bucklandi of Liassic age, a series of beds rich in plants of Jurassic age, and beds of Cretaceous age containing Trigonia and many other fossils.
The Heteroptera can be traced back farther than any other winged insects if the fossil Protocimex silurica Moberg, from the Ordovician slates of Sweden is rightly regarded as the wing of a bug.
The next member of the series is a mass of coarse sandstones, with some slates and a few thin coals, known as the Millstone Grit, which is about equally developed in England and in Scotland.
In Karagwe certain quartzites, slates and schistose sandstones resemble the ancient gold-bearing rocks of South Africa.
The Louisiade and the d'Entrecasteaux Islands consist of the same slates and schists as form the main axis of the eastern peninsula, and they are auriferous.
It appears to consist in the main of a continuation of an axis of old schists and slates, with granite intrusions, and flanked by coastal plains with Cretaceous or Jurassic, and Miocene beds, with Pleistocene sands and reefs and volcanic rocks.
Geologically the region is made up of Carboniferous limestones, clay slates and sandstones, containing anthracite and coal; of Cretaceous marls, chalk, sandstone and greensands - chalk cliffs, in fact, accompany the Don for 200 m.; and of Miocene limestones and clays.
The rocks in the Arakan range and its spurs are metamorphic, and comprise clay, slates, ironstone and indurated sandstone; towards the S., ironstone, trap and rocks of basaltic character are common; veins of steatite and white fibrous quartz are also found.
Whilst pyrites is found abundantly in the older crystalline rocks and slates, marcasite is more abundant in clays, and has often been formed as a concretion around organic remains.
The Maitai beds include a thick mass of slates and sandstones, which form the bulk of the Southern Alps, whence branches extend southeastward to the coast.
Machinery, wool, cloth, chicory, slates, &c., are also produced.
Slates and fine-grained sandstones appear here freely through the glacial drift.