Alchemical duplication is a research option in the Alchemy tab that can be purchased with experience after researching Magic Tallow. Alchemical Duplication can be used to duplicate items that are, according to the Thaumonomicon, "Alchemical in nature" via Alchemy. Items that can be duplicated are: gunpowder. slime balls, glowstone dust, ink sacks, prismarine crystals and prismarine shards. All duplication recipes use the item being duplicated as their catalyst.
Gunpowder has both Alchemical and mundane uses, and can be annoying and difficult to acquire without causing their main source, the creeper, to explode. As such, creating gunpowder via Alchemy can make a Thaumaturge's life much simpler, eliminating the need for outing to hunt and kill creepers. Gunpowder can be duplicated with 4 Ignis and Perditio aspects using gunpowder as the catalyst.
Slime balls have uses in both the mundane and magical world as an adhesive agent, but are rather difficult to acquire unless one is in the proper areas. Regardless of this, they are much easier to create than to hunt for in the wild, making this a worthwhile recipe. Slime balls can be duplicated with 1 Victus and 2 Aqua aspects using a slime ball as the catalyst.
Glowstone dust has its share of mundane and Alchemical uses just as the rest of previously mentioned substances. It can also be equally as difficult to get, with the a trip to the Nether being dangerous and inconvenient, and witch hunting equally as much so, yet more impractical. This, along with the others, makes this recipe worthwhile for the practical Thaumaturge. Glowstone dust can be duplicated with 1 Sensus and 3 Lux aspects using glowstone dust as the catalyst.
Ink sacks have a few mundane and magical uses, however, their main purpose to a Thaumaturge is as ink to fill one's Scribing Tools, as well as to create them. This makes them very important for research. It can, however, be tedious or annoying to swim to the nearest river, lake, or other sufficiently sized body of water to hunt for squids, and equally as much so to retrieve their ink sacks. This recipe allows for one to research in the comfort of their own home without having to risk their life for a few drops of ink. Ink sacks can be duplicated with 2 Sensus and Aqua aspects using an ink sack as the catalyst.
Prismarine crystals have no Alchemical uses, but can be used to create the sea lamp, a water-proof light source that emits a light level of 15. However, they have few uses outside of this and are difficult to obtain, making this recipe, although less useful than others, still a great method of avoiding the danger of venturing to the more hostile areas in the world of Minecraft. Prismarine crystals can be duplicated using 1 Aqua, 1 Lux and 2 Vitreous aspects using prismarine crystals as the catalyst.
Prismarine shards have no Alchemical uses, but can be used to create many of the variants of prismarine blocks, which can be used for decoration, and the sea lamp, which is a water-proof light source that emits a light level of 15. Prismarine shards can usually only be obtained by venturing to sea temples, difficult due to the powerful guardians who guard their halls, and the fact that they are underwater. Prismarine shards can be duplicated with 1 Terra and 2 Aqua aspects using prismarine shards as the catalyst.