13I shall now speak of purple, which, above all other colours, has a delightful effect, not less from its rarity than from its excellence. It is procured from the marine shell which yields the scarlet dye, and possesses qualities not less extraordinary than those of any other body whatever. It does not in all places where it is found possess the same quality of colour; but varies in that respect according to the sun’s course.
2Thus, that which is obtained in Pontus and in Galatia, from the nearness of those countries to the north, is brown; in those between the south and the west, it is pale; that which is found in the equinoctial regions, east and west, is of a violet hue; lastly, that which comes from southern countries possesses a red quality: the red sort is also found in the island of Rhodes, and other places near the equator.
3After the shells are gathered they are broken into small pieces with iron bars; from the blows of which, the purple dye oozes out like tears, and is drained into mortars and ground. It is called ostrum, because extracted from marine shells. Inasmuch as this colour, from its saltness, soon dries, it is prepared for use with honey.