They are at a depth of about 12 ft., in slaty shale containing Llandeilo fossils and contemporaneous felspathic ash and scoriae.
In colour Anopheles is usually brownish or slaty, but sometimes buff, and the thorax frequently has a dark stripe on each side.
Lichens for the herbarium should, whenever possible, be sought for on a slaty or laminated rock, so as to procure them on flat thin pieces of the same, suitable for mounting.
When first born these are clothed with a uniform slaty-grey fur, which in due course gives place to a coat of more tawny hue than the adult livery.
In a second phase of the species, the colour, which often displays a slaty hue (whence the name of blue fox), remains more or less the same throughout the year, the winter coat being, however, recognizable by the great length of the fur.
From the name schistos, and the mode of formation, there can be little doubt that this species was the salt which forms spontaneously on certain slaty minerals, as alum slate and bituminous shale, and which consists chiefly of the sulphates of iron and aluminium.
Blue mud, according to Murray and Renard, is usually of a blue or slaty or grey-green colour when fresh, the upper surface having, however, a reddish tint.
The origin of slaty cleavage is in some measure obscure.
Flattening of particles by compression, orientation of particles by flow and formation of laminar crystals, the fundamental explanation of slaty cleavage is found.
In 1854, after the meeting of the British Association in Liverpool, a memorable visit occurred to the Penrhyn slate quarries, where the question of slaty cleavage arose in his mind, and ultimately led him, with Huxley, to Switzerland to study the phenomena of glaciers.
It occurs crystallized, commonly in cubes, in schistose and slaty rocks, and less abundantly in the younger sedimentary deposits.
Although called blue, the colour is a slaty or drab tone.
The plumage is generally inconspicuous: some tint of brown, ranging from rufous to slaty, and often more or less closely barred with a darker shade or black, is the usual style of coloration; but some species are characterized by a white throat or a bay breast.
Buffaloes of an uncouth appearance and of a dark slaty color, strikingly contrasting with the neat cattle, abound in Egypt.
The colour is a slaty black; the hide is immensely thick, with scanty hairs.
Gneisses, schists, slaty rocks.