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NOME XXI. STEATITE, WITH ARGIL.

[STAHLITE, from Stahl, 1700.]

Dr. Babington informs us, that this substance is harder, and less unctuous, than common steatite, and has an earthy smell when breathed

on.

That of Cornwall is of a dark olive-green colour, and slaty texture*.

NOME XXII. OLLITE, WITH SILEX.

[POTTALITE, from Pott, of Berlin, who first analysed stones and earths, 1730.]

This kind is described by Mr. Kirwant. The quartz is in many parts visible in the veins, and the lustre approaches that of graphite.

Cat. St. Aubyn, p. 118.

+ i. 376.

NOME XXIII. SERPENTINE, WITH SIDERITE.

[BLACOLITE, from Black, 1760.]

This compound is usually of a blackish colour, and the fracture rather foliated, or striated. That of Portsoy is of a greenish black*.

NOME XXIV. SERPENTINE, WITH BASALTIN.

[BERGMANITE, from Bergman, 1780.]

This substance is black, and the fracture splintery. It might perhaps be classed among the Sideromagnesian Rocks.

NOME XXV. LIME-STONE, WITH ARGIL. [KLAPROTHITE, from Klaproth, 1790.]

This combination sometimes occurs in marbles; for example, in that of Campan in the

Bab. ut supra.

Pyrenees, which from its remarkable structure however may partially be classed among the Anomalous Rocks. Its decomposition in the air, so visible in the pillars of the palace at Trianon, is owing to the mixture of argil, which imbibes moisture. Karsten, in his description of Leske's Museum, mentions granular limestone, mixed with clay-slate, from Kunnersdorf, in Upper Lusatia,

HYPONOME I.

Marble of Campan, &c.

Micronome 1. Lime-stone, with argil.

NOME XXVI. LIME-STONE, WITH GYPSUM.

[LAVOISITE, from Lavoisier, 1790.]

This sometimes occurs at Montmartre, near Paris. It is a small proportion of lime, naturally intermixed, which renders the plaister of Paris so much superior to other manufactories of that substance.

HYPONOME I.

Massive.

HYPONOME II.

Schistose.

NOME XXVII. LIME-STONE, WITH SILEX. [BERTHOLITE, from Berthollet, 1800.]

Concerning the calcareous stones Mr. Kirwan observes, that "when mixed with siliceous particles in considerable proportion, they effervesce with acids but slightly and slowly, and their fracture tends to the conchoidal, but often also to the earthy; of this we have a remarkable instance in Leske, s. 229. Its lustre, O. Hardness, scarcely 9. Fragments, 3; which indicates the siliceous ingredient. Its sp. gr. only 2,254; which shows it to be of the nature of sand-stone. Heated to 141°, it did not form a lime, nor did it melt. When the lime-stone is of the granular kind it has more lustre, and is much heavier, see Leske, s. 1098. But when the particles of silex are in a smaller proportion, or not purely siliceous, the lime-stone presents

a different appearance: thus the lime-stone, Leske, s. 1769, seems as if passing into hornstone, and is of a yellowish grey colour. Lustre, 0. Transparency, 1. Fracture, fine, splintery. Fragments, 1. Hardness, 9. Sp. gr. 2,640. It effervesces briskly with acids, but melts into a greenish grey compact enamel.

"Effervescence with acids is not therefore a sufficient proof that a stone will burn to lime: thus the dark bluish-grey stone, Leske 0. 1229; whose lustre is 0; transparency, 0; fracture, uneven and splintery; fragments, 2; sp. gr. 2,740; hardness, 9; and which contains the impressions of various shells, and effervesces very briskly with acids, yet melts into a black compact glass. It has an earthy smell when breathed on."*

NOME XXVIII. GYPSUM, WITH MARL. [VAUQUELITE, from Vauquelin, 1800.]

Gypsum often forms veins in hardened clay or marl, and is sometimes penetrated with the latter substance, Instances may be found at the Old Passage, near Bristol.

Kirwan, i. 373.

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