In German, the stone called _Donnerkeil_ (thunderbolt) has several synonyms; among these is _Storchstein_ (“stork-stone”). It is evident that the stone of Heracleis was identical with the precious and brilliant variety of _cerauniæ_ mentioned by Pliny, “which drew to themselves the radiance of the stars.” The flashing and ruddy light of the ruby suggested an igneous origin, and induced the belief that rubies were generated by a fire from heaven,—in other words, by the lightning flash.[239] The analogy between the flame of a lamp or the glow of a burning coal and the radiance of a ruby, suggested some of the names given to this stone, or those resembling it in color, as, for instance, the Greek _anthrax_ and the Latin _carbunculus_ and _lychnis_. Probably the fancy that such stones were luminous in the dark was nothing more than the logical result of the quasi-identification of them with fire in some of its manifestations. Still, it is a well-known fact that some stones possess a high degree of phosphorescence. This circumstance must have been observed by chance, and may have had something to do with the legends of luminous stones, although this peculiarity is not characteristic of the ruby. According to Pliny, the lychnis, perhaps a spinel, was so called _a lucernarum accensu_ (from the lighting, or the light, of lamps). The author of the poem “Lithica” says that the diamond (_adamas_), like the crystal, when placed on an altar, sent forth a flame without the aid of fire.[240] If this did not refer to the use of rock-crystal as a burning-glass, we might see in the passage an indication that the phosphorescence of the diamond had already been noted before the second or third century of our era. From the Lydian river Tmolus a marvellous stone was taken which was said to change color four times a day. This surpasses the properties of the “saphire merveilleux” which changed its hue at night. Only innocent young girls could find the Lydian stone, and while they wore it they were defended from outrage.[241] Is it possible that the ancient writer intended to hint at the proverbial fickleness of woman, when stating that this changeable stone could only be discovered by one of the fair sex? The temple of the Syrian goddess Astarte contained an image of this divinity crowned with a diadem in which was set a luminous stone. Such was the splendor of the light emitted by this gem that the whole sanctuary was lighted up as though with a myriad of lamps. Indeed, the stone itself bore the name _lychnos_ (“lamp”). In the daytime this light was fainter, but was still very noticeable, as a fiery glow.[242]