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A little chain of rocks, amidst the eternal snows of Mont Blanc, consists of laminar black or green siderite, felspar, and graphite, with a little quartz and mica*

NOME III. SIDERITE, UNCTUOUS QUARTZ,

PYRITES.

Mont Broglia, a southern spur of Mont Blanc, is of a stone softer than granite, being a mixture of siderite, felspar, mica, unctuous quartz, and pyritest.

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NOME IV. PORPHYRY, WITH CHALCE.

DONY.

The green porphyry, in particular, sometimes appears spotted with chalcedony, so as to assume the form of a composite rock*. Ferber, it has been already observed, saw numerous blocks of green porphyry at Ostia, the sea-port of Rome, where they had been disembarked in ancient times, and neglected after the empire fell a prey to barbarians.

NOME V. JASPER, WITH AGATE AND

CHALCEDONY.

This curious rock is described, by Petrini, as consisting of these three substances, in veins of white, green, red, yellow, purple. It admits a beautiful polish, and is found at Monte Rufole, in the Volterranot.

In the noble collection of Besson, at Paris, there is a specimen joined with pure transparent quartz, which had probably passed as a vein through the rock.

† Gabinetto Nazareno, Roma 1792, 2 vols. 8vo. ii. 258.

NOME VI. MICA AND ACTINOTE.

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A composition rather uncommon, but found in primitive regions, abounding in mica slate.

Mica and actinote, from Mount St. Gothard.

NOME VII. ACTINOTE, SIDERITE, MICA.

A composite rock of delphinite or actinote, greenish siderite, felspar, and white mica, all in little grains or plates *.

NOME VIII. QUARTZ, SIDERITE, OXYD

OF IRON.

A rock, composed of quartz, siderite, mica, and oxyd of iron; together with a tabular felspar, which he calls sanidine, a substance in silky tufts, which he calls desmine, and another resembling spinel, which he calls spinelan, was discovered by Nose on the banks of the lake of Laach, near Andernach. See his mineralogy of the mountains of the Rhine, quoted in the Jour

Sauss. § 1293.

nal de Physique for August, 1809. This singular rock might be called Nossite, from the name of the discoverer.

NOME IX. QUARTZ, SCHORL, AND LIME

STONE.

This composition appears in the infinite variety of the Alps.

NOME X. QUARTZ, LIME-STONE, AND

SAUSSURITE.

Also found in the Alps. Besides Saussurite (that is, basaltin with a notable proportion of magnesia), quartz and schorl may also be found, conjoined with steatite and other magnesian rocks.

NOME XI. FELSPAR, QUARTZ, GARNETS.

This rock sometimes constitutes mountains, and may be found in Switzerland, Sweden, and Scotland.

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NOME XII. FELSPAR, QUARTZ, TALC.

This noble rock contains plates of splendid talc, varying in size from half an inch to many feet in diameter. It chiefly occurs in the Uralian mountains, whence talc has sometimes been called Muscovy glass.

NOME XIII. FELSPAR, FIBROUS SIDERITE.

A rock in confused veins of felspar, white mica, and green fibrous siderite *.

NOME XIV. FELSPAR, CALCAREOUS SPAR.

A rock of great rarity, and seldom occurring except in the ejections of Mount Vesuvius, which also affords a composite stone of felspar, garnets, and actinote; with other aggregations on which it would be tedious to enlarge. Nor is it certain that they occur in such masses as to constitute rocks. Many may be mere parasites or vein stones.

Sauss. $ 1359.

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