Chap. HI.
ON STONE.
703
Statuary Marble—primitive Limestone . — Of this entire mountains are sometimes formed :in other instances it is found in beds; its specific gravity is 2*7 ; it can be sawn into thinslabs, and will receive a brilliant polish : these qualities are only found in three varietiesof limestone, the saccliaroid, foliated, and the carboniferous : it never contains the remainsof organised bodies, but sometimes quartz, mica, hornblende, and other substances.
The white marble of Carrara is a fine grain, even and close, of equal colour, resemblingwhite sugar; crystals are occasionally embedded in it, which prevent the working of thechisel: when diversified with spots and greenish or greyish veins, it is called Cipollinaccio ;that of a coarser grain resembling salt, and thence called Saligno , is more difficult to work,and often contains a great deal of moisture: those which sound like a bell under the toolare called Campane; being exceedingly dry they are very hard. As these marbles areblasted, it is common to find them shaky in the interior of their mass, and containingveins: the Carrara marble will not admit of so fine a polish as that of Paros , but mostmodern statues are formed of it; probably the situation of the quarries affording greaterfacility for the working and transport. The Paros statuary is milk-white, greyish, andopaque; its texture varies from fine-grained to coarse; it is more difficult to work thanthe fine Carrara. The true Paros , with crystalline grains, is that which the Homanmasons called Marmo greeo a specchioni; that which they designated Paros is probablyCoralitique. Pliny says that several marbles exceeded the Paros in whiteness; the Lunior Carrara had this advantage over it; but as this was the case with several others, itwould be difficult to decide which were from Carrara and which from the Greek quarries.The works executed in Parian marble retain all the delicacy of wax with the soft lustre oftheir original polish.
Hie Pentelican marble obtained from the mountains in the neighbourhood of Athens,and exclusively used in the temples there, is of a yellowish white, close-grained, frequentlyinterspersed with greenish stripes, which causes it to decompose when exposed to the air;it is found in beds, and so easily separated that the ancients used it as bricks and tiles;the Romans call it Marmo cipolla; but it must not be confounded with the Cipollino, ormarble of Caryste, which is undulated from a greyish white to green, and Is not astatuary marble. The quarries at Pentelicus were admirably situated both for -workingand transporting the blocks of which the beautiful structures at Athens were constructed ;being at a considerable elevation, a regular inclined plane was made from the entrance ofthe quarry to the city, and masses of marble were moved upon rollers with little labour,care only being required to guide them. The various tinted marbles, or those havingcoloured veins, are of the same crystalline character, affected by an oxide of iron; but theblue and green tints are occasioned by minute particles of hornblende, as in the slate bluevariety called Turchino. The black marbles receive their dark colour from charcoal mixedoccasionally with sulphur and bitumen.
The Giallo Antico is a beautiful marble, of a regular yellow colour with light violet veins;it is extremely rare, and is supposed to have been brought from Numidia ; there areseveral varieties ; the black marble of the ancients called after Lueullus, from his havingintroduced it, was a very fine unmixed black ; when exposed to a high temperature in anopen crucible it burns white; with sulphuric acid it forms a black-coloured mass, andwhen dissolved in nitrous and muriatic acids it leaves an insoluble black-coloured substance ;it is composed of
Lime
.
-
- 53-38
Carbonic acid
.
_
-
-
- 41-50
Black oxide of carbon
.
.
.
- *7 5
Magnesia and oxide of manganese -
-
-
-
•12
Oxide of iron
_
-
-
•25
-
-
-
-
1-13
Sulphur
-
-
-
-
•25
Potash and water, &c.
2-62
100 00
The Rosso Antico is an Egyptian marble, the quarries of which are said to have been onthe borders of the Red Sea ; the best specimens are of a deep red without either black orwhite veins ; the grain is very fine, compact, and takes a fine polish ; it seems to be dottedor strewed over with very fine grains of sand. It has been occasionally used for thepurpose of sharpening tools; pieces of it for this application have been found in theexcavations of Herculaneum and Pompeii .
The Verde Antico is a kind of brescia, whose base or cement is a mixture of talc andlimestone, the dark green fragments consisting of serpentine with spots of a lighter shade,pure white and fine black ; the colours should be very distinct to constitute a fine specimen.It was found in Laconia and Thessalonica ; several columns are extant, of great beauty andof large dimensions.