Crystallized Carbonate of Lime, inverted

The upper figure is a curious specimen of crystallized carbonate of lime, with the faces of the rhomb in the inverse order to the laminæ of the nucleus, and their angles so near to those of the primitive, over which it is formed, as to look like the same, differing only in one degree: 102° 30′, 77° 30′. This is from Pwll-y-cochan, near Conway, Carnarvonshire, out of a lead and blend mind. It is stained probably with oxid of iron. The edges are more transparent and shining than the other parts. The rest of the mass or matrix is crystallized in primitive rhombs, mingled so confusedly that it is not readily perceived without breaking; when they are found very regular.

The lower figure is from the summit Moel y hiraddwg, a lofty hill bounding the vale of Clyde, and was sent me by D. Pennet, Esq. F.R.S. F.L.S. withs ome nearly like the above. This is a specimen of a more confused crystallization, the red oxid being very abundant. The crystallized parts are separated in irregular columns of a romantic appearance: the little white strata at the bottom have settled between the red ones in a curious manner. The fracture is irregular, depending on the confused laminæ, the light falling on the flat sides of which occasions a shining lustre.