Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/90



I shall now proceed to describe the mineral substances which I observed in Sky, having reserved these details for separate consideration, lest they should interrupt the connection of the geological remarks which form the preceding part of this paper. The most numerous, and not the least interesting of these minerals, are those of the zeolite family. They are to be seen in various parts of the island, but are to be found in the greatest beauty and variety in the cliffs of the western shore between Loch Bracadale and Loch Brittle. Talisker, as it is the most accessible of these places, so it presents the richest assortment to the collector of specimens. But in general the mineralogist can have no access to any specimens but those which fall from the cliffs, and have long been exposed to the violence of the sea and the injuries of the air. However splendid therefore, they my once have been, they are not always to be found in a state of good preservation. It is moreover often difficult to gain access to them on any terms, particularly along the other points of this wild shore, since it is so beset with rocks on which a dangerous surf is almost always breaking, that it requires neither common good weather, nor common dexterity in the management of a bear, to effect a landing and retreat without hazard.

Analcime is the most commons of all these minerals on the shore to which I have new alluded, and it is found in the greatest profusion at Talisker. It sometimes occupies cavities of considerable size, in different varieties of the trap, but seems to be by far the most abundant in those, earthy and little compact sorts, for which there is no name in our catalogue of terms. In other cases it forms flat druses of considerable extent, occupying the walls of fissures, while in a third, a single crystal is sometimes seen in a cavity just sufficient to contain it. In the greater number of instances the remaining part of such cavities is filled with the filamentous mesotype