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First Part

OF MARBLES IN GENERAL

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SECTION FIRST.


OF THE FORMATION, QUALITIES, BEAUTIES, AND DEFECTS OF MARBLE.

1. Marble, according to every analysis which has been made of it, is a calcareous stone of different degrees of hardness, of a fine grain, often colored, and always susceptible of polish. As among other calcareous stones, there are Marbles of the first, second, and perhaps of the third formation. The old Marbles are not, like the new, composed of simple stony particles, reduced by the action of water into minute molecules; they are formed, like other ancient stones, of fragments of stones still more ancient, and the most of them are mixed with shells and other marine productions. All are deposited in horizontal beds, or parallelly inclined, and differ only in colors from other calcareous stones; for there are some stones which are almost as hard, as dense, and as fine grained as Marbles, to which, nevertheless, this name is not given, because they have no decided color, or rather, no diversity of colors. These colors, although very deeply imprinted in certain Marbles, do not change their nature in other respects; they add nothing to their hardness or density, nor do they prevent their calcination and conversion into lime by the same degree of heat as with other hard stones.

Stones which are of a fine grain and susceptible of polish, form a link between the common stone and Marbles; all are of the same nature, since all effervesce with acids, all break in granulated fragments, and all can be reduced to lime.

I say all, because I speak only here of pure Marbles, that is, of those composed entirely of calcareous matter, with no admixture of clay, slate, lava, or other vitreous materials; those which are largely mixed with these heterogeneous substances are not true Marbles, but demi-stones, to be separately considered.

2. The beds of old Marble were formed, like other calcareous beds, from the deposit of the sea, small quantities of stony substances, shells, gravel, pebbles, &c., being washed together and stratified. The local establishment of most of these beds of Marble of ancient formation seems to have preceded that of other beds of calcareous stones, as they are almost always found beneath such beds, and, in a hill composed of twenty or thirty beds of stone, there are usually but two or three, often but one, of Marble; these always lie beneath the others and near the clay which forms the base of the hill, either resting upon it, or only separated from it by another bed which seems to be the residuum of all the others, being made up of Marble, pyrites, and a large quantity of sparry crystallizations.

Thus, by their situation beneath the other beds of calcareous earth, these old Marbles have received the colors and petrifying fluids which the water always collects in its passage through the vegetable earth and the beds of stone which intervene between this and the Marble beds. These first formations of Marble are distinguished by several characteristics. Some bear the prints of finely marked shells; others, as the Lumachella, or fire-marble, seem composed of small snail-shaped shells; others contain belemnites, fragments of madrepores, &c. These Marbles bearing the imprints of shells are less common than the Breccias, which contain few marine products, but are made up of pebbles and rounded flints, joined with a stony cement, forming angular fragments when broken, whence this name.

3. These Marbles of the first formation may be divided into two classes, the first comprising those called Breccias, and the second, the Shell-marbles. Both contain veins of spar, yet they are more frequent and more apparent in the shell-marbles, than in the Breccias. What the artisans call "flaws" in blocks of calcareous earth, are also small veins of spar, and the stone often breaks in the direction of these flaws while working it with the mallet; yet sometimes this spar acquires so much solidity, especially when mixed with combinations of iron, as to offer as much resistance as the other material.

4. The analysis of the substance of White Marble, and the sparry grains which are perceived in breaking it, seem to demonstrate that it was formed by the distillation of water. It is also worthy of notice that, when worked, it yields equally to the mallet in every direction, whether cut horizontally or upright, while Marbles of the first formation can be worked horizontally with greater ease than in any other manner. These colors can be easily perceived in the quarries, or on the rough blocks. Their immersion in water draws out the colors, and gives them for the monument, as much lustre as the highest polish.

5. There are but few Marbles, of much bulk at least, which are of a single color. Some fine black and white specimens are the only ones which can be quoted, and even these are often tinged with grey or brown. All others are of various colors. It may, indeed, be said that every shade of color is visible in Marbles. We have red with its various shades, orange yellow and yellowish, green and greenish, blues, more or less decided, and violet. These last two colors are the most rare, yet they are seen in the Violet Breccia, and in the Bleuturquin, a Marble obtained from Genoa and several other quarries, and particularly suited to furniture and chimney pieces. From the mingling of these colors results an infinitude of shades in the grey, dove, whitish, brown, and blackish Marbles.

6. The natural brilliancy and intensity of the colors of Marble can be increased by art. For this end it is only necessary to heat them. The red will become more vivid, and the yellow will change into an orange or vermilion. The heat necessary to work this change is acquired by polishing them till hot, and the shades of color brought out in this simple manner are permanent, and remain unchanged by cold or time; they are durable because deeply imprinted, and the entire mass of Marble would receive this increase of colors by an intense heat.

7. The ground, which is generally of a uniform color, should be distinguished from those parts which are stained or veined, often with different colors; these veins traverse the bottom, and are rarely intersected by others, they being of a later formation than the bottom, and only filling crevices caused by the waste of the first material. In the same manner, the stains are rarely traversed by other stains unless by a few threads of herborizations of a still later formation, the sole difference and it should be remarked that these stains terminate irregularly, with broken edges, while the veins are neither indented or broken, and are usually distinctly marked through their course.

It often happens that portions differently colored, and differently marked with spots and veins, are found in the same quarries, and sometimes in the same block; yet in general, the marbles of a country resemble each other more strongly than those foreign to them. This peculiarity they have in common with other calcareous stones which are of the same texture and of different grains.

8. There are some rough Marbles which are worked with difficulty, resisting the tools of the workmen, and often breaking into splinters. Some others of a softer nature crumble instead of splintering. Many others are filled with cavities; some are traversed by numerous threads of a tender spar, and are called by the workmen Stringy Marbles.

9. The Italian Marbles are very numerous, and are more celebrated than any European Marbles. That of Carrara, which is white, is taken from the coasts of Genoa in blocks of an unlimited size. It has a crystalline grain, and is comparable in purity to the ancient Marble of Paros.

The Marble of Saravezza, which is found in the same mountains as that of Carrara, is a still finer grain; a red and white Marble is also found there, with red and white spots distinctly marked; this Marble resembles a Breccia, and is called Brocatello; a blackish tint is also sometimes seen in it. Its quarry is almost as continuous as that of Carrara, and of all other white or colored crystalline Marbles found in Sienna, or in the Genoese territories; all of these are found in large masses, in which no indication of shells is to be seen; a few crevices are there, filled up by a crystallization of calcareous spar. No doubt all these Marbles are of second formation.

The environs of Carrara also furnished two kinds of Green Marble; one, incorrectly termed Egyptian Green, is of a deep green, with white and flaxen grey spots; the other, called Sea Green, is of a clearer color, veined with white.

10. The White Marble of Paros is the most renowned of antique Marbles. The great artists of Greece employed it in those exquisite statues which we still admire, not only for the perfection of the workmanship, but also for their preservation during more than twenty centuries. This Marble is found in the isles of Paros, Naxos, and Tinos. Its grain is coarser than that of Carrara, and it is mixed with a great quantity of small crystals of spar; these cause it to crumble easily while working, and it is also these which give it almost as great a degree of transparency as alabaster, which it resembles in softness.

11. In Spain, as well as in Italy and Greece, there are hills, entire mountains even, of White Marble. A kind is also found in the Pyrennes, on the side of the Bayonne, which is similar to the Marble of Carrara, with the exception of the grain, which is coarser, and which gives it a strong resemblance to the white Parian Marble; but it is softer than the last, and its white often takes a yellowish tinge. Another Marble of Greenish-brown, spotted with red, is also found in the same mountains.

In the suburbs of Molina, a flesh-colored and white Marble is found, and about a quarter of a league from there, others, red, yellowish, and black, and grained like that of Carrara, but these quarries are quite scarce.

12. The marble called Antique Breccia seems a sort of calcareous pudding-stone, composed of large pieces distinctly rounded, some of which are white, blue and red, and others black. This variety of colors gives a beautiful appearance to this Marble. The breccia of Aleppo is also composed of rounded pieces of dove-color. The Breccia of Saravezzia presents rounded fragments of a very large size, the most of which are violet; the others white or yellowish.

All the calcareous pudding-stones are varieties of Breccias, and no distinction would have been made between them, did they not usually differ in their cement, which is softer, and unsusceptible to polish. Only one more degree of petrifaction is needed to make them perfectly similar to the finest Breccias, as the cement of these pudding-stones composed of vitreous flints needs but one shade of petrifaction to be converted into a material as hard as porphyry or jasper.



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