One of the more useful magic item components is red coral from the Mediterranean Sea. In Mythic Europe, what do scholars think coral is? Would they know it is an animal? Would they assume it is a plant because it behaves like one? Or would the calcium deposits just be another rock? If magi want to conjure up a sample of red coral for making anti-demon wards, the difference between Creo Animal, Creo Herbam, and Creo Terram is pretty vast. Or would the naturally occurring coral have a special aspect to it that can't be duplicated by hermetic magic at all?
Herbam maybe? Greek mythology has seaweed or reeds turned into coral by blood from Medusa's head, according to https://en.wikipedia.org/wiki/Precious_coral.
The most common form that people / magi would encounter is would be its dead form. So I think that most would consider it to be a rock / mineral. Just like some crystals seems to be growing straight out of the rock. Only after someone spend enough time to study it would you be able to conclude that it would be something else.
The medusa's blood turning reeds or seaweed to coral would also indicate that they would think it is a rock / mineral. As the Medusa turns people to stone when they are looked upon. I don't think any one would argue that they are still organic despite them being living persons before the medusa looks upon them.
Here's an extract from the Wikipedia page on coral:
"In his Scala Naturae, Aristotle classified corals as "zoophyta" ("plant-animals"), animals that had characteristics of plants and were therefore hypothetically in between animals and plants. The Persian polymath Al-Biruni (d. 1048) classified sponges and corals as animals, arguing that they respond to touch. Nevertheless, people believed corals to be plants until the eighteenth century, when William Herschel used a microscope to establish that coral had the characteristic thin cell membranes of an animal."
I like the idea, that upon their death red corals change into semi-precious gemstones.
If players ask for an argument, Ovid Metamorphoses Book IV Verses 753–803 is a good one. But my motivation is, that with that ruling trade, crafting, enchantment (ArM5 p.97 box Material and Size Tables) and handling with magic (ArM5 p.152 Terram Spells) of red corals all work to my satisfaction without further coral-specific rules in the saga.
I found this entry on the topic
And that begs the question: If it's a Zoophyte so can we use both Animál OR Herbam or only the lowest score between both?