Trichrus[1] comes from Africa: it is of a black colour, but yields three different liquids, black at the lower part, blood- red in the middle, and of an ochre colour at the top. Thelyrrhizos[2] is of an ashy or russet colour, but white at the lower part. Thelycardios[3] is like a heart in colour, and is held in high esteem by the people of Persia, in which country it is found: the name given to it by them is "mule." Of thracia[4] there are three varieties; a green stone, one of a more pallid colour, and a third with spots like drops of blood. Tephritis[5] is crescent-shaped, with horns like those of the new moon, but it is of an ashy colour. Tecolithos[6] has all the appearance of an olive stone: it is held in no estimation as a gem, but a solution of it will break and expel urinary calculi.