Next among the white stones is "asteria,"[1] a gem which holds its high rank on account of a certain peculiarity in its nature, it having a light enclosed within, in the pupil of an eye as it were. This light, which has all the appearance of moving within the stone, it transmits according to the angle of inclination at which it is held; now in one direction, and now in another. When held facing the sun, it emits white rays like those of a star, and to this, in fact, it owes its name.[2] The stones of India are very difficult to engrave, those of Carmania being preferred.