Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/100

 88 which are all hexahedral prisms, terminated at each extremity by a hexahedral pyramid. These crystals, all of which belong to the elongated variety of the primitive crystal, arc placed edgeways on the quartz, and though this specimen has been several years in my collection, several of the crystals of laumonite still retain some degree of transparency.

In the collection of Mr. Richard Phillips I have seen a very fine specimen from Paisley in Renfrewshire, in which the laumonite is grouped with analcime, and I have a small specimen from Portrush in the County of Antrim, in which it occurs with stilbite and analcime.

I possess a specimen of amygdaloid having avery argillaceous and earthy base, from the Venetian States, the nodules of which are all hollow, and have their interior surface lined with very small crystals of this substance, of a dull white appearance, and very friable.

Lastly, I have a specimen of prehnite, of a slightly yellowish green colour, the crystals of which are grouped together and penetrate each other in such a manner as to form spheroids; these have their surface covered by a dull white and pulverulent laumonite. This specimen, which was given me as coming from China, has for its gangue an earthy argillaceous rock of a greenish grey colour.

Thus, with this, as with many other mineral substances, it has ceased to be found the exclusive production of a peculiar district, as soon as attention has been particularly directed towards it. It may be observed however, from what I have stated, that the laumonite affects the zeolitic rocks more than any others; and that wherever these exist, we may hope to meet with it.

I have said, under the head of specific characters, that the laumonite