In the mica-schists of this group biotite or muscovite may be the principal mineral and often both are present in varying proportions; the mica has developed from the argillaceous matter of the original rock; in addition there is always quartz and sometimes felspar (albite or oligoclase).
Their arid country was the best safeguard of their cherished liberty; for the bottle-shaped cisterns for rain-water which they excavated in the rocky or argillaceous soil were carefully concealed from invaders.
The plain, sandy in its northern part, is in the south a deep bed of argillaceous marl, scattered over with great granite boulders and fragments of greenstone.
Calc-schists are usually argillaceous limestones in which a large development of biotite or phlogopite has occasioned foliation.
It is not volcanic, but consists of argillaceous schist and quartzite.
Pliny shows that for this purpose the gold was placed on the fire in an earthen vessel with treble its weight of salt, and that it was afterwards again exposed to the fire with two parts of salt and one of argillaceous rock, which, in the presence of moisture, effected the decomposition of the salt; by this means the silver became converted into chloride.
It has been variously attributed to metamorphism, consequent upon igneous intrusion, earth movements and other kinds of geothermic action, greater or less loss of volatile constituents during the period of coaly transformation, conditioned by differences of permeability in the enclosing rocks, which is greater for sandstones than for argillaceous strata, and other causes; but none of these appears to be applicable over more than limited areas.
Schleissen, to split), in geology, a fissile, fine-grained argillaceous rock which cleaves or splits readily into thin slabs having great tensile strength and durability.
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.
Argillaceous brown iron ore is often known in Germany as Thoneisenstein; but the corresponding term in English (clay iron stone) is applied to nodular forms of impure chalybite.
The more argillaceous and the less siliceous the soil the more readily can balls of earth be retained about the roots.
Argillaceous or clay soils are those which contain a large percentage (45-50) of clay, and a small percentage (5 or less) of lime.
Laterite is a ferruginous and argillaceous rock, varying from 30 to 200 ft.
At Rammelsberg in the Harz it forms a bed in argillaceous schist, and at Mansfeld in Thuringia it occurs in the Kupferschiefer with ores of nickel and cobalt.
The geological core of the system consists of primitive argillaceous schists, capped by quartzite and broken through in places by basalt.
There was not a stone to be seen up to the base of the Andes; the river banks were of argillaceous earth and the bottom of fine sand.
A good sandy loam is common in the Heath division; a sandy loam with chalk, or a flinty loam on chalk marl, abounds on portions of the Wolds; an argillaceous sand, merging into rich loam, lies on other portions of the Wolds; a black loam and a rich vegetable mould cover most of the Isle of Axholme on the north-west; a well-reclaimed marine marsh, a rich brown loam, and a stiff cold clay variously occupy the low tracts along the Humber, and between the north Wolds and the sea; a peat earth, a deep sandy loam, and a rich soapy blue clay occupy most of the east and south Fens; and an artificial soil, obtained by "warping," occupies considerable low strips of land along the tidal reaches of the rivers.
Red and grey sandstones, hornblende and argillaceous schist are found in the mountains, porphyry and basaltic rocks also occur; sulphur and fuller's earth are worked.
In marls, cement-stones and argillaceous limestones); (4) sulphide of iron, as pyrite or marcasite (when finely diffused, giving the clay a dark grey-blue colour, which weathers to brown - e.g.
Yellow ochre); (6) sand or detrital silica (forming loams, arenaceous clays, argillaceous sandstones, &c.).
As the impurities increase in amount the clay rocks pass gradually into argillaceous sands and sandstones, argillaceous limestones and dolomites, shaly coals and clay ironstones.
Any argillaceous material, which can be used for the manufacture of bricks, may be called a brick-clay.
In addition to the reddish or brownish argillaceous matrix it contains fresh or decomposed crystals of volcanic minerals, such as felspar, augite, hornblende, olivine and pumiceous or palagonitic rocks.
To be of service the lime should be what is known as "hydraulic," that is, not pure or "fat," but containing some argillaceous matter, and should be carefully slaked with water before being mixed with the aggregate.