Crystallized Carbonate of Lime

After having figured the modifications at tab. 436, I was highly pleased at finding this singular specimen from the same neighbourhood, in the collection of the Count de Bournon, who so readily lends his assistance to the advancement, of a science in which he eminently excels. I have specimens of the equiaxed modification accumulated in parcels forming the metastatic: this present is an accumulation of crystals of the twenty-seventh modification of the Count de Bournon’s work, also forming a compressed metastatic crystal with two of its opposite faces, very broad, and is curiously surmounted with one, and covered with more crystals which are nearly simple dodecaëdrons (being two obtuse six-sided pyramids joined base to base) passing to those distinctly divided by, or forming the apexes to, six-sided prisms or columns longest at the middle of the specimen. I have represented the dodecaëdron in the left hand figure; and the other figure shows these faces in conjunction with faces nearly approaching the metastatic or thirty-sixth modification of the Count dc Bournon; and it may be observed that the series of obtuse dodecaëdron begins with the twenty-fourth, and continuing nine modifications ends at the thirty-third, which is here shown in conjunction with the twenty-seventh, upon the primitive rhomb.

The present specimen is admirably instructive in a geological point of view, as the same neighbourhood produces many similar varieties of these specimens, and shows that certain modes of crystallization are somewhat local.