Alchemy is nothing else but the set purpose, intention, and subtle endeavor to transmute the kinds of the metals from one to another. According to this, each person, by his own mental grasp, can choose out for himself a better way and Art, and therein find truth, for the man who follows a thing up more intently does find the truth. It is highly necessary to have a correct estimation of stars and of stones, because the star is the informing spirit of all stones. For the Sol and Luna of all the celestial stars are nothing but one stone in itself; and the terrestrial stone has come forth from the celestial stone; through the same fire, coals, ashes, the same expulsions and repurgations as that celestial stone, it has been separated and brought, clear and pure in its brightness. The whole ball of the earth is only something thrown off, concrete, mixed, corrupted, ground, and again coagulated, and gradually liquefied into one mass, into a stony work, which has its seat and its rest in the midst of the firmamental sphere.
Further it is to be remarked that those precious stones which shall forth-with be set down have the nearest place to the heavenly or sidereal ones in point of perfection, purity, beauty, brightness, virtue, power of withstanding fire, and incorruptibility, and they have been fixed with other stones in the earth. They have, therefore, the greatest affinity with heavenly stones and with the stars, because their natures are derived from these. They are found by men in a rude environment, and the common herd (whose property it is to take false views of things) believe that they were produced in the same place where they are found, and that they were afterwards polished, carried around, and sold, and accounted to be great riches, on account of their colours, beauty, and other virtues. A brief description of them follows:
The Emerald. This is a green transparent stone. It does good to the eyes and the memory. It defends chastity; and if this be violated by him who carries it, the stone itself does not remain perfect.
The Adamant. A black crystal called Adamant or else Evax, on account of the joy which it is effectual in impressing on those who carry it. It is of an obscure and transparent blackness, the colour of iron. It is the hardest of all; but is dissolved in the blood of a goat. Its size at the largest does not exceed that of a hazel nut.
The Magnet Is an iron stone, and so attracts iron to itself.
The Pearl. The Pearl is not a stone, because it is produced in sea shells. It is of a white colour. Seeing that it grows in animated beings, in men or in fishes, it is not properly of a stony nature, but properly a depraved (otherwise a transmuted) nature supervening upon a perfect work.
The Jacinth Is a yellow, transparent stone. There is a flower of the same name which, according to the fable of the poets, is said to have been a man.
The Sapphire Is a stone of a celestial colour and a heavenly nature.
The Ruby Shines with an intensely red nature.
The Carbuncle. A solar stone, shining by its own nature like the sun.
The Coral Is a white or red stone, not transparent. It grows in the sea, out of the nature of the water and the air, into the form of wood or a shrub; it hardens in the air, and is not capable of being destroyed in fire.
The Chalcedony Is a stone made up of different colours, occupying a middle place between obscurity and transparency, mixed also with cloudiness, and liver coloured. It is the lowest of all the precious stones.
The Topaz Is a stone shining by night. It is found among rocks.
The Amethyst Is a stone of a purple and blood colour.
The Chrysoprasus Is a stone which appears like fire by night, and like gold by day.
The Crystal Is a white stone, transparent, and very like ice. It is sublimated, extracted, and produced from other stones.
As a pledge and firm foundation of this matter, note the following conclusion. If anyone intelligently and reasonably takes care to exercise himself in learning about the metals, what they are, and whence they are produced: he may know that our metals are nothing else than the best part and the spirit of common stones, that is, pitch, grease, fat, oil, and stone. But this is least pure, uncontaminated, and perfect, so long as it remains hidden or mixed with the stones. It should therefore be sought and found in the stones, be recognized in them, and extracted from them, that is, forcibly drawn out and liquefied. For then it is no longer a stone, but an elaborate and perfect metal, comparable to the stars of heaven, which are themselves, as it were, stones separated from those of earth. Whoever, therefore, studies minerals and metals must be furnished with such reason and intelligence that he shall not regard only those common and known metals which are found in the depth of the mountains alone. For there is often found at the very surface of the earth such a metal as is not met with at all, or not equally good, in the depths. And so every stone which comes to our view, be it great or small, flint or simple rock, should be carefully investigated and weighed with a true balance, according to its nature and properties. Very often a common stone, thrown away and despised, is worth more than a cow. Regard must not always be had to the place of digging from which this stone came forth; for here the influence of the sky prevails. Everywhere there is presented to us earth, or dust, or sand, which often contain much gold or silver, and this you will mark.
Coelum Philosophorum, Paracelsus