This section is from the book "An Experimental History Of The Materia Medica", by William Lewis.
Corallium rubrum Pharm. Lond. Red coral: a hard, brittle, branched substance, resembling the stalk of a plant; usually about the thickness of a goose quill; full of knots; sometimes straighti, and sometimes variously bent; both externally and internally of a deep bright red colour. It is found adhering to rocks and other bodies in the sea, particularly in the Mediterranean; covered with a soft fungous bark, in which is a great number of cells curiously divided, containing a milky juice, with apertures on the surface: this cortical part is separated while fresh and soft. It has been generally referred to the vegetable kingdom; but is more probably, like the preceding, the work and the nest of little animals.
Red coral appears to have for its basis the same calcareous animal earth as the corallines and the shells of sea fifties: like them, it is changed by calcination into quicklime, dissolves in all acids except the vitriolic, and is precipitated by this last from its solutions made in the others. It is used also, like those productions, as an absorbent of acid humours in the first passages; and like them, when satiated with such acids as are generated in the bodies of animals, it forms therewith a restringent saline compound. That it has any virtues distinct from those of the other calcareous absorbents, or that it is superiour in absorbent power to the cheaper testaceous bodies, there are no grounds to sufpect.
The levigated coral is sometimes counterfeited in the shops with the common teslacea coloured with dragons blood or red bole. These abuses may be discovered, by shaking the powder with water and suffering it to fettle, when the white and the coloured matter will separate from one another and appear in great part distinct: dragons blood may be known likewise by its giving a red tincture to spirit of wine; and bole, by its retaining its redness in the fire, whilst coral burns white.
Corallium prasparatum Ph. Lond.