porous. It takes a good polish. Its specific weight never exceeds 2-3.
What is most extraordinary with regard to this substance is, that it adheres to the tongue, because it imbibes humidity easily.
immersed in water, it immediately gives out little bubbles of oxygen ;
these were in the pores, which soon fill with water, rendering it thus
clear and bright until dried up again by contact with the air.
It is found in China, Arabia, Egypt, the Feröe Isles, Hungary, Silesia, Saxony, Piedmont, and in Trance.
When analysed, it gives