that of a vase, it would become one of the most beautiful materials of the arts.

"There is another variety of this rock, with little globules very near each other, but offering the same system of formation. This, according to M. Rampasse, appears in different parts of the chain of Niolo, in Corsica, being far more common than the former; but very curious, because in the fractures may be easily discerned the mode of formation of the globules, which are the result of a particular system of crystallisation. The oxydation of the iron having diminished the force of the cohesion of this rock, it is difficult to obtain large pieces. The same cause has occasioned shades of different colours; while the size of the globules does not exceed four or five lines in diameter. Their formation approximates to that of the variolites of Durance; but their crystallisation is more decidedly enounced than that of the latter."

From this last description it seems doubtful whether the petals appear in the latter kind. As the flowers of the former bear no small resemblance to the marigold, caltha, it was imagined that Calthite might be a proper appellation: but if in the smaller kind no petals appear, the name of Niolite may be preferable;

Name.

especially as Niolo is celebrated for various beautiful stones*.

Description.

NOME III. CORSILITE.

This beautiful rock being also from Corsica, it was thought proper to propose a geographical name; and an island so eminent in the history of the rocks, well deserves this distinction.

The rock now in question is a most beautiful mixture of greyish white, with the most delicate emerald green, which presents at the same time a satiny appearance. According to Werner, it is a mixture of felsite, or compact felspar, with actinote. Among the Italian artists, it has been long known by the name of Verde di Corsica ; and Ferber, in his intelligent travels through Italy, 1772, informs us that "the Verde di Corsica is no marble, but a hard rock, striking fire with steel, of a white substance, with blackish or violet spots, and large grass-green sherl crystals, of a sweet colour. Large tables of this fine

Even in the large maps of Bacler Dalbe, Corsica must be imperfectly represented, for Niolo, and other names often mentioned, are not to be found.

stone are to be seen in the Capella di S. Lorenzo, at Florence."

remarks.

Saussure, who discovered pebbles of this rock Saussure's among those of the lake of Geneva (which include many curious substances brought by the Rhone, and its confluent streams, often from inaccessible parts of the Alps), and afterwards found it in its native places, describes it as composed of jad and a new substance which he calls smaragdite, from smaragdus, the Latin name of the emerald. He found it in the mountain of Musinet, near Turin, which also presents the curious semiopals, called hydrophanes: and which chiefly consists of serpentine, and other magnesian rocks. In another spot also, among magnesian rocks, he found the same substance; but the smaragdite was of a grey colour*. In Corsica it is found in detached masses, which encumber the bed of the rivulet of the village of Stazzona, and which came from the mountain of Santo Piatro di Rostino, not far from Orezza. Hence it has also been called Verde antico di Orezza. It is also found in large detached masses at Voltri, near Genoa; and a similar rock is found at Estendorf, in Stiria. The same com

Sauss. § 1313, 1362. See his account of smaragdite, § 1313. He observes, that oriental jad is very fusible.

Sites.

position is found at Serviere, above Briançon; but the diallage, or smaragdite, is black, yellow, bronze, grey, or silver-grey*. In other instances, the diallage has a metallic splendour; and the author has a specimen, which he received from Faujas, of a rock composed of serpentine and felspar, containing metallic diallage; and which was discovered by the Marquis de Cubieres, in the ruins of Pompeia; so that scarcely a beautiful rock can be said to have escaped the researches of the ancients: and the ruins of Rome are found to present about two hundred and fifty kinds, while those of London would only afford white marble.

The

The most complete account of the beautiful rock here called Corsilite, may be found in Patrin's ingenious system of mineralogy. Smaragdite. smaragdite, he observes, was formerly called mother of emerald; and sometimes appears to have passed even for emerald itself. This substance is a singular combination of many constituents, as may be judged by the following analysis, by Vauquelin, of the green and grey smaragdite; a name which might be retained as a compliment to its great observer, and as the green is its most usual and beautiful colour.

* Brard, ii. 309.

The increase of weight arises from the oxygen, which has been absorbed by the metallic oxyds during the operation.

In his recent publication, Haüy places the Diallage. green diallage as a variety of the strahlstein of the Germans, while he regards the metalloid diallage, or that with metallic splendour, as the schiller spar and Labrador hornblende of many mineralogists, the schillerstein of Werner, and the bronzit of Karsten. He has also found a palpable transition from the fairest green to the grey metallic splendour*. As this interesting substance rivals the gems in beauty, its description will not be found prolix.

The base of this rock has, by Saussure, been called a jad; by Werner, a compact felspar; by Haüy, from its toughness, a tenacious felspar. The substance called jad, has been recently di

Jad.