PICROLITE. 637 Constituent Parts. According to Ilausmann, it is principally composed of Carbonate of Magnesia. Observations. The above is all the information I have been able to collect in regard to the appearance of this species. It was first described by Ilausmann, and he proposes to place it in the system beside Serpentine. It is here placed at the end of the Talc Family, where it can re main until its true place be ascertained. END OK VOLUME FIRST;