Lithomarga Enlarge
Feb. 1. 1808. Publish’d by Ja.s Sowerby London.
British Mineralogy
CCLII
Quartzum Lithomarga

Lithomarga

  • Class 2. Earths.
  • Order 2. Mixed.
  • Syn.
    • Lithomarga. Kirw. 1. 187.
    • Argile lithomarge, Argilla crustacea. Waller, 1. 49.
    • Stein-mark. Emmerl. 1. 355.
    • La Moelle de Pierre, ou la Lithomarge. Broch. 1. 447.

Ireland affords many curious substances, and seems to abound with some varieties of this. The present specimens are all from thence, by favour of Dr. Scott of Dublin. The beauty of some of them gives me an idea of the Lithomarga called Terra miraculosa, and may be, perhaps, equally beautiful.

The uppermost specimen is soft, and marks on paper readily and smoothly. The middle one is not quite so smooth, while the lower one is more earthy and rather gritty. It is remarkable for its purplish cast, probably caused by a mixture of the red and black Oxides of Iron.

The middle figure is coloured with red Oxide of Iron, holding the little whitish waxy granular fragments of almost perfect Steatite, as Trapp sometimes does Zeolite.

The lower figure is of a brighter purple than the upper one, and the little specks of a similar waxy Steatite give it a remarkable and pretty appearance. Some of these, Dr. Scott informs me, are of a nature to bear turning in a lathe. They are found in the county of Antrim; some pear Temple-patrick, accompanying the Basalt in the Dykes, which from its crumbling state is provincially called Rottcn-rock. An exposure to moisture will naturally produce this effect on the softer mixed Steatites, as well as on Lithomarga.

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