Crystallized Carbonate of Lime

The simple hexaëdral column is among the scarcer forms of this substance in Britain.

The present specimens came from Cumberland. Crystals of this form more rarely occur in Derbyshire. In Scotland they are found at Strontian with Stilbite on the opposite side of the specimen, as figured at tab. 258. In some instances the whole form of the crystals is very neat, and every face is polished.

The upper specimen has not the end face polished, but roughish.

The lower specimen is most extraordinary, as on it the crystals have very short columns and lie in various directions, having both ends opaque, but are smooth and polished on all the faces. The cause of polished faces might seem to depend upon the gradual separation of the menstruum or solvent from which it crystallized; and a great quantity might, by suddenly passing off, leave the terminations of the crystals rough as in the upper specimens, which are not finished at both ends; the lower crystals probably derive their opacity from a scanty supply of water of crystallization at the ends.

Some of the crystals in the upper specimen have the terminal edges bevilled towards the column which leads to other formations—see the next figure.