Agate
Agate is a variety of quartz known as chalcedony found in red and white rock known as ribbon; moreover, its variety of milky white can be artificially colored to bright green, blue, or greyish purple. The four important types of agates are fire, moss, carnelian, and tree agate. Both moss and tree agate are oftentimes ornamented by Nature with the distinct forms of ferns and clouds, thus, giving the quartz an abstract effect. Moss agate was believed to be good for sight, so physicians used palettes of this stone to mix ingredients for making ointments. While representations of vegetation made of iron and magnesium oxides are formations found in tree agate, the other varieties of agate are determined by layers. The parallel lines of dark and light tint are called ribbon or banded agate. Pliny was a great believer in agate and wrote that by burying these stones one could avoid storms; however, as the popularity of agate being used as a talisman increased, the demand for agate used for signets decreased during the Roman Era.
Girolamo Cardano tested the talismanic worth of agate in the 16th century. He kept a journal of good or ill effect of the gemstone on his fortunes. He concluded the agate was no good and abandoned it after a string of bad luck that he was unable to otherwise explain. One of the beliefs vested in agate was the protection against poisons specifically the poison of a scorpion or snake. While it was common to claim a virtuous stone could protect the bearer from a poison, whether he set out to test this particular piece of medical lore is not known to me. Cups and bowls were sometimes carved from agate such as those belonging to the emperor Constantine. These bowls were created for the virtues of strength and prudence. One may conclude the natural virtues of agate were imparted to the contents of the bowl by touch. Moreover, the signet rings of the Roman Era were used as seals and were intaglio so left a raise impression on wax. The distinction between the magic of an image and the virtue imparted by a mineral becomes important. A talisman carved on the gemstone is an artificial engraving by the magician giving it uniqueness. One can be critical of the virtue of a magician so one may also be himself critical about the virtues of the stone; although, the tradition of carving a protective image date all the way back to the cylindrical seals of Babylon.
Throughout the Middle Ages "the agate" was known by a different sign, namely the "achates". Camillo Leonardi mentions the achates nine separate times in his medieval lapidary and another stone called the "gagates" three separate times. Interestingly, gagates was grouped because of its magnetic property with amber for its electrical property. Anyhow, the virtue of the achates stone was derived according to The Mirror Of Stones from the river Acheas since the agate stone was mined in Sicily. Similar information had been reported by Theophrastus who also said agate sold for a high price; thus, the region from where the stone was mined adds to its reputation. Other sources say Marbode of Rennes derived the name from the Aeneid because Achates was the companion of Aeneas. For this reason, some correspondence was made between nature (the river Achaea) and literature (the Aeneid by Virgil) emerging from the belief that Aeneas carried an agate gemstone.
"Achates is a Stone of divers Colours, which are varied according to the Place of its Generation; of which there are many Species, but the most famous are these Seven, which, as Jewellers affirm, are not only varied in Colour, but even in their Virtue."
The Indian achates was said to have formed with the images of beasts, flowers, woods, or birds. It was the agate with the property against venom. The Arabian achates variegated with colors that tended toward transparency. The coral agate was thought to carry a magnetic charge. All agates were said by Camillus Leonardi to make men solicitous though the proper virtue of an agate arise from its place of origin. The seven places where agates were mined are ranked by him as follows: Sicilian, Cretan, Indian, Egyptian, Persian, Arabian, and Cyprian. The locality of a stone was believed to give it a kind of savor particular in nature. For ease of understanding, the difference was listed by color. Therefore, one may assume every locality had its particular color of agate.
Stones generally were thought to emerge from earth either by conflux or percolation then set on fire and burnt resulting in a dry, smoky condition. While the names are strange, the observations of stones emerged from mining. Red ochre was used for pigment by painters. One could assume kyanos was used for blue. The different ochres were added to earthenware before kilning giving its color. For this reason, Theophrastus concluded that art imitated nature. The production of the Ptolemy Cameo (278–269 BC) demonstrates his point, since the images carved from the stone were discovered in a natural state, according to Albertus Magnus who visited the shrine of the Three Kings. He said, "I have proved that this is not glass but stone; and therefore I have assumed the picture was made naturally and not artificially." In a translator's note, Dorothy Wyckoff theorized the images might be the likenesses of Alexander the Great and Olympias, his mother. Sardonyx is an agate as well as the birthstone for August. It was popular with Roman soldiers who wore rings of sardonyx engraved with the image of Mars. Sardonyx also was popular with Roman women who wore cameos engraved with the image of Venus.
In conclusion, agate in its variety of forms has foundations in the productions of signet rings and cameos beginning with the Roman era. The Book Of Minerals (published 1250) expressed some controversy in discussing image magic and the production of images on stones as natural, artificial, or both. The question of an image's authenticity emerged from different worlds: one, the Christian lapidary; two, the lapidary of magic and astrology; or three, scientific lapidary. The Ptolemy cameos compared with Constantine's cups imply no conflict existed between the realms of superstition and Christianity.
Camillus Leonardus (1451 – 1550) was an Italian astronomer, mineralogist, and physician. Although the topics of his works mainly deal with the occult power of gems and their engraved images, he also created astronomical tables verifying the position of fixed stars and published astrological rules for the administration of drugs.
Albertus Magnus (1193-1280) was instructed in the writings of Aristotle before taking-on orders. He became a Dominican about the year 1223 and studied theology. As a master of theology, he was able to become a professor at the University of Paris where Thomas Aquinas studied under him. Of the many topics that were included in Albert Magnus’s writings; astrology, mineralogy, and alchemy were part of a corpus on natural sciences. For the most part, he became known as a magician after his death for his study of alchemy.
Girolamo Cardano (1501 – 1576) was a mathematician, astrologer, and physician educated at the University of Padua. He was a public lecturer at Milan in 1534, the a professor of medicine at Bolongna in 1562. However, he was arrested for debt in 1570 subsequently moving to Rome the following year. During his lifespan, Cardano wrote over 100 books.