Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/99

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But on further examination I find this substance occurring in specimens from various other places. I have in my possession a specimen from the Island of Ferröe, in which pretty large crystals, of a dull white aspect, and almost pulverulent, but of which the figure is still perfectly discernable, are grouped with stilbite in larger crystals, and not in the least altered, on a layer of quartz about three lines thick, enclosing a nucleus of that sort of argillaceous and earthy rock, well known as the gangue of the zeolites of Ferröe, and from which it is separated by a thin layer of green ferruginous earth. The exterior surface of this quartzose layer, on which the crystals of laumonite are placed, is covered by a vast quantity of small crystals of stilbite, differing in figure from those of the same substance that accompany the laumonite, the forms of both of which belong to the very numerous series of crystals of this substance, that have not yet been described.

I have another small group of laumonite also from Ferröe, the crystals of which, unmixed with any other substance, are placed on a small layer of granular quartz of a loose texture, the grains of