We will see that these three Sciences (Alchemia, Archemia, and Spagyria) are not so distant from one to another and joined together, they are necessary in order to conduct the Magnum Opus and to generate the Lapis Philosophorum.
Archemy is a Science, maybe not so Glorious than the Science of Alchemy, but not to be taken so lightly. Yes it IS a Science, and even an incredible one. Do you know we can create long burning lamps with a modified olive oil ? That we can create "Graduating Oils", in which, precipitated metals are bring to perfection after a moment of maturation ? That we can make perpetual mines of running animated Mercury for the Magnum Opus ? That it is possible to make a such pure and revived lead, that, once melted,it's looking like gold, and once cold, it's covered, not by oxide, because there is no possible oxidation now, but by a kind of green skin ?
That is is possible to predict the climat with a special barometer (Fitzroy stormglass is one kind of), but also, to know if someone, anywhere in the world, is well or not, dead or alive, with a kind of barometer (wet method) or a lamp (dry method). When the flask broke, or the light of the flame do not shine, the person is dead. That you can multiply in quantity, anykind of metal ? Making it grow slowly whitout any effort ! That it is possible to create a growing metallic tree, giving flower and little apples of ... gold, the FamousWomen Alchemist Mme D'Urfée showed one to Casanova when he came to see her for the first time. She said it was only for fun. You can also create special metallic glass, 100% of metal, no kind of salt or anything else in it. These glasses, a blue one and a red one, creating a purple color to the sun, can transmute quicksilver into gold, process that happens in some French Cathedrals during the summer solstice... the Stances of Dzyan, cited in the Secret Doctrine of H.P.Blavatsky are very old documents ... protected by a Particular, (opposite to a universal), this product/matter is able to protect paper or a sheet from oil, fire, water, sun etc etc, making it almost indestructible ! There is also the fabrication of living creatures in all realms, like artificial plants, pearls, gems, living metals (like the tree of Mme D'Urfée), salts, and animals or humans, this is called the Homonculus. This last part seems very "dark", but in fact, this is a very high creation, and a manifestation of the All Power of the Alchemist in this realm, incarnating the faculty of giving LIFE to all realms, alike it's creator ! Manifesting it's own Deity in matter and the world of Illusion. This can lead to a profound awakening and understanding of our own's Nature and Nature Herself. This is the same thing, expected it is in the astral, when a Magus create a Spiritus Familiaris. Tibetan Monks can also use these methods of creating an entity, which lead to the understanding that all that is created is in fact imaginary ... even ourself. The Alchemist is here a Bringer of Life, of Light, an Agent of Fire and not a creator of Darkness since the moment it's intentions are Toward the Divine and it's Manifestation in matter of via Himself. The limit with Darkness here is very fragile ... this is why this part of Alchemy/Archemy is very secret, hidden. This is not a Path for every Alchemist.
All these particulars are very interesting, and can be really helpfull.
And even more, at the end of the Magnum Opus, White or Red, when you want to make your Universal a Particular (because you make an Orientation, Orient = Or in french mean gold) and make a transmutation, you need to know some little things about Archemy if you want to cure metals, and Spagery in order to cure animals and humans.
As you can see Archemia do not stop at the production of Gold (for making money, but also, and foremost, for the Magnum Opus, in order to have Gold for the several process involved). Some texts give recipes (partially veilled sometime, or not very prolific in gold) in order to make a living for the True Seeker of the Stone, because some process are long, and require a constant attention (remember that in 16th century, no hot plate with thermo regulators, no pyrex, only blown glass and firewood) you had to be in the Lab constantly.
No, it's not a Science of vulgar puffers, the later can also do Alchemy for Gold only, and not 'God' only.
We should not consider Archemia as a bastard Science, taken between Spagyria and Alchemia.
Puffers and bad alchemists created a bad aura around this marvellous science. And those who spit on Archemy/Voarchadumia, are simply ignorant persons. Look how much texts are on Archemia in old books, a lot ! An often, mixed with methods for the Metallic Stone.
Spagyria is a Science of Extraction, in order to make potable Principles by plants or metals, gems, and any kind of animal matters. Creating the Long Life Elixir from the Philosopher Stone, need to master techniques of Spagyria, and mastering some laws of extractions. Spagyria is very close to Alchemy, like Archemy is, but the distinction is made because of the difference between some process, change the process and then you do Alchemy. In my opion, you cannot really learn the Magnum Opus de Alchemia in Spagyria.
It is used for plants (rarely, but making grow faster a seed was also practiced), animals and humans, but since the moment you cure the leprosy of a metal, by graduating it to gold, then you do Archemia. Here Spagyria is more a Science of Mercuries, in order to take out Sulfurs and to make them if possible, maturing.
We call High Spagyria the method of metallic extractions of Sulfurs, in order to make remedies for humans and animals. Spagyria is also used for simple extraction of essential oils of plants by distillations, and also the creation of perfumes.
So yes, two Minor Sciences of importance, at the service of the Major one, Alchemy.