Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/94



In the same place I found nodule of great size, and of a variety which is far from common, but which has I believe been found in the Faroe islands. The nodules in question are either hollow or solid, and sometimes reach the enormous dimension of four and even five feet. The hollow ones are crystallized within in the fasciculated forms already described. The peculiarity of this variety consists in its extreme frangibility: the least effort is sufficient to detach the plates of which its structure is formed, and it therefore falls to pieces in the very act of procuring it, unless great care is taken; its fracture is fresh, and distinguished by an uncommon degree of the pearly lustre which is so characteristic of this mineral. So great is its frangibility, that the jarring of the hammer at one end of a large nodule is often sufficient to destroy the whole; and it not unfrequently happens, that when a large piece is obtained entire and has been laid down, although it appears uninjured and resists a strong effort of the hands to break it, yet in a few minutes it falls to pieces with a sort of violence not unlike that which is known to happen in unannealed glass that has received an injury. This variety is sometimes white, and much resembling spermaceti in its translucency, but in the greater number of cases it is of a delicate flesh colour.

The next of these minerals is mesotype, and it is found in three states, a compact, a mealy, and a crystallized form. Of these the compact varieties sometimes recede so far in character from the mineral in its most acknowledged forms, that it is only by tracing the gradation of the several varieties, that we are enabled to determine the names of those which occupy the distant points of this range. The opake whiteness, the toughness, and the radiated disposition of those specimens which may be considered as forming the first remove, serves to connect them with the best characterized