Granite

“ The rock here is a sort of sand or pudding stone; there is no limestone or granite. And all the hills are tree-covered. To many this clothing of verdure is most restful and pleasing. I missed the sharp outlines, the delicate artistic sky lines, sharply defined in uplifted bare granite peaks and ridges, with the purple and violet color of the northern mountains, and which it seems to me that limestone and granite formations give. There are none of the great gorges and awful abysses of the White Mountains, both valleys and mountains here being more uniform in outline. ”

“ Granite, it has been just said, exists most commonly in masses; and these masses are rarely, if ever, incumbent on any other rock: they are the basis on which others rest, and seem, for the most part, to rise up from under the ancient, or primary strata. The granite, therefore, wherever it is found, is inferior to every other rock; and as it also composes many of the greatest mountains, it has the peculiarity of being elevated the highest into the atmosphere, and sunk the deepest under the surface, of all the mineral substances with which we are acquainted. ”

“ There must have been from two to five miles of other rock lying upon the stuff that crystallized into granite. A wrinkling in the skin of the earth exposed the granite, a wrinkling so gradual that doubtless if generations of men had lived on top of the wrinkle they would have sworn it did not move. ”

“ We saw quantities of small pieces of various sorts of granite, and porphyry scattered over the plain, which had been carried down by a torrent, probably from quarries of ancient ages; these were white, mixed with black spots; red, with green veins, and black spots. After this, all the mountains on the right hand were of red marble in prodigious abundance, but of no great beauty. They continued, as the granite did, for several miles along the road, while the opposite side was all of dead-green, supposed serpentine marble. ”

“ When magnified and examined with the polariscope, a thin section of granite is a very beautiful object, and its different constituent parts stand revealed with the greatest distinctness: we at once learn to see the crystals of feldspar, somewhat opaque and cloudy as they usually are in granite, but now and then clear and beautifully striped, and also the crystals of mica, imbedded in the clear quartz, which will be at once known by its bright clear colors and by the margin of rainbow-like tints which border its patches. ”

“ We think of granite as a firm, imperishable kind of rock, and use it in great buildings like churches and cathedrals that are to stand for centuries. But the faces that are exposed to the air suffer, especially in regions having a moist climate. The signs of decay are plainly visible on the outer surfaces of these stones. Fortunate it is that the weathering process cannot go very deep. ”

“ The granite, though pervious, is so to a very limited extent when compared with limestone, and through a granite country there are no springs that issue from subterranean reservoirs. All the rain that falls on the surface runs off superficially, but not all at once, for on the granite lie enormous beds of peat, the growth and decomposition of moor plants through vast ages. ”

“ After a little they turned off toward a tremendous rock of solid granite that had been cleft smoothly in twain by some gigantic force of nature, and, walking between the towering walls of stone, came out on the farther side upon a small level space, where immense ferns and flags grew thickly in the rich soil, held in place and kept damp by the great cool masses of stone. ”

“ GRANITE. This familiar rock may be studied as an example of the second great group of rocks,—the unstratified, or igneous rocks. These are not made of cemented sedimentary grains, but of interlocking crystals which have crystallized from a molten mass. Examining a piece of granite, the most conspicuous crystals which meet the eye are those of feldspar. They are commonly pink, white, or yellow, and break along smooth cleavage planes which reflect the light like tiny panes of glass. Mica may be recognized by its glittering plates, which split into thin elastic scales. ”

“ The lowest stratum of the earth which human labour has arrived to, is granite; and of this likewise consists the highest mountains of the world. It is known under variety of names according to some difference in its appearance or composition, but is now generally considered by philosophers as a species of lava; if it contains quartz, feltspat, and mica in distinct crystals, it is called granite; which is found in Cornwall in rocks; and in loose stones in the gravel near Drayton in Shropshire, in the road towards Newcastle. ”

“ Granite.—A true granite consists of a crystalline-granular rock consisting of quartz, felspar (orthoclase) , and mica; the quartz is the paste or ground-mass in which the felspar and mica crystals are enclosed. This is the essential distinction between a granite and a quartz-porphyry or a granophyre. ”

“ On the contrary, all our evidence tends to show that the formation of granite, like the deposition of the stratified rocks, has been successive, and that different portions of granite have been in a melted state at distinct and often distant periods. One mass was solid, and had been fractured, before another body of granitic matter was injected into it, or through it, in the form of veins. Some granites are more ancient than any known fossiliferous rocks; others are of secondary; and some, such as that of Mont Blanc and part of the central axis of the Alps, of tertiary origin. ”

“ Nature and Qualities of the Rocks.—The granite is the most prevailing, as well as the most striking in its appearance and texture, in the whole range. Mineralogically considered, every specimen is a gem. Granite is a compound, aggregate rock, here of a lively flesh or rose color, consisting of perfectly formed crystals of quartz, feldspar, mica, and in some instances hornblende, when it merges into what is termed syenite. ”

“ Every geologist knows that granite is a rock which could only have been formed and consolidated at great depths. When, therefore, such a rock occurs at the surface, it is evidence beyond all doubt of prodigious erosion. The granite has been laid bare by the removal of the thick rock-masses underneath which it cooled and consolidated.
A glance at any map of Scotland will show that many river-valleys, and not a few lakes, of the Highlands have a north-east and south-west trend. This trend corresponds to what geologists call the strike of the strata. ”

“ The granite shaft is made out of the original substance of the earth's crust. Its minerals are the elements out of which all of the rock masses of the earth are formed, no matter how different they look from granite. Sandstone is made of particles of quartz. Clay and slate are made out of feldspar and mica. Iron ore comes from the hornblende in granite. The mineral particles, reassembled in different proportions, form all of the different rocks that are known. ”

“ The third, or Redruth patch of granite, affords many varieties of this rock, and has been well explored by numerous mines which have been productive in both tin and copper ores, affording also to the mineralogist a great variety of rare specimens. But the fourth, or Land's End granite, is by far the most important to the geologist, for the land becoming here very narrow, the sea has produced cliff-sections, both in the granite, and also at its point of junction with the slate, exhibiting many interesting phenomena. ”

“ Great masses of the strata which the granite has invaded are often floated off, and are found lying in the heart of the granite much altered by the heat to which they have been exposed, and traversed by the igneous rock in ramifying threads. Such granite intrusions are generally known as bosses from their rounded surfaces, and the frequency with which they form flattish dome-shaped hills, rising above the older rocks surrounding them. ”

“ The fundamental rock is granite (In several places I observed in the granite, small dark-coloured balls, composed of minute scales of black mica in a tough basis. In another place, I found crystals of black schorl radiating from a common centre. Dr. Andrew Smith found, in the interior parts of the country, some beautiful specimens of granite, with silvery mica radiating or rather branching, like moss, from central points. At the Geological Society, there are specimens of granite with crystallised feldspar branching and radiating in like manner.) ”

“ What are the various modes in which granite exists, is a question not absolutely decided among mineralogists. 1. That it exists as a schistose stone of a fissile texture, in gneiss and veined granite, is on all hands admitted, though in this state the name of granite is generally withheld from it. 2. That it exists often without any indication of a fissile texture, and altogether unstratified, is likewise acknowledged. 3. That it is found in veins, intersecting the strata, has been shown above. ”

“ This granite is intermixed with harder and more resistant rock masses, which remain as gigantic boulders all over the granite mountains as the softer parts are washed away. In the interior and to a less extent on the coast, limestone formations, coal measures and tertiary sandstones occupy large areas. ”

“ The granite is curiously concealed under a thousand formations and surfaces, under fertile soils, and grasses, and flowers, under well-manured, arable fields, and large towns and cities, but it{281} makes the foundation of these, and is always indicating its presence by slight but sure signs. ”

“ At other times the granite would appear to have been erupted amongst the aqueous strata, for these are highly confused, and baked, as it were, at their junction with the granite, from which, also, long veins are seen protruding into the surrounding beds. Metamorphic granite, then, graduates, as a rule, almost imperceptibly into rocks which are clearly of aqueous origin; while on the contrary the junction-line between igneous granite and the surrounding rocks is always well marked. The origin of granite, however, is a difficult question, and one which has given rise to much discussion. ”

“ If we imagine common granite coarsely pounded, and thrown into a vessel of water, it will arrange itself at the bottom of the vessel in a condition very much like that of gneiss, which is indeed nothing else than stratified granite. ”

“ The united and increasing action of the winds and waves has worn the hard granite rock into the most fantastic forms, and from certain points of view it is not difficult to invest some of these masses of stone with a fancied resemblance to the human form. ”

“ But wherever they can be seen to any extent, they exhibit a great degree of irregularity, the different kinds of rock being found in large masses confusedly heaped together. The granite chiefly occurs in the lower part of the hill, and the veins of it, which penetrate the other rocks, become more slender as they ascend, in all those places where they can be distinctly traced. ”

“ Hence the sculptor of granite is forced to confine himself to, and to seek for, certain types of form capable of expression in his material; he is naturally driven to make his figures simple in surface, and colossal in size, that they may bear his blows; and this simplicity and magnitude are exactly the characters necessary to show the granitic or porphyritic color to the best advantage. ”

“ Each of these insulated groups of granite is surrounded by schistose rocks, the layers of which, on all sides, incline from the granite at various angles, from 20° to 40°. Although these groups are thus separated from each other by the slate at the surface, yet it is the general opinion that they gradually approach beneath, until they are all united into one and the same mass—the intermediate hollow spaces (the valleys, as it were, between the granitic mountains) being occupied by the slate. ”

“ Granite which we thus see irrupted through and into the stratified rocks, is, in fact, of no one particular or determinate age, but is the local result and evidence of many independent excitements or periods of critical action among the subterranean agencies of heat. We may, therefore, consistently admit granite, as well as other igneous rocks, to be of any, that is, of all ages; some of that which is visible in the crust of the globe may have been solidified from fusion before the production of any of the strata ”

“ The summits of the Rocky mountains are formed entirely of primitive rocks, chiefly of granite itself. A red and saline sandstone rests on this granite, through the whole chain, as far as it has been explored. ”

“ Now, if we examine a fragment of the oldest or fundamental gneiss or granite, we shall see glassy grains of quartz, reddish or white flat-surfaced crystals of felspar, and dark-coloured prisms of hornblende. When destitute of any arrangement in layers, the rock is granite; when arranged more or less in flakes or laminæ, it is gneiss, the structure of which may arise either from its having been formed in successive beds, or from its having been flattened or drawn out by pressure. ”

“ There is no reason, however, to suppose granite original, more than any other composite rock, although we may be ignorant of the particular process in which it is formed, and although, comparatively in relation to certain other rocks, granite, or certain masses of this composition, may be found of a more ancient date. ”