As an additional thought, the use of extra magnitudes for unnatural property could possibly be used to create rocks, metals and gems that don't exist in nature. Looking at what is under Muto Terram guidelines, I find the following:
Level 3: Change dirt so that it is slightly unnatural (requisites may be required).
Level 4: Change dirt so that it is highly unnatural (requisites will often be required).
I think the question I would try and weigh as a gamemaster when assessing the ritual, is whether 1) the type of dirt / stone / metal / gem is slightly unnatural or whether it is highly unnatural; 2) from there, whether I would require a requisite.
To give an example, I might consider allowing a Creo Terram ritual spell to, for example, create a slightly unnatural rock, metal or gem, provided the proposed material doesn't fall outside the scope of what is possible for a rock, metal or gem to be like. As examples, I might give the following:
- for example, a gem that has the hardness of diamond, a shade of purple, and an affinity (for the purpose of S&M) that is much like sapphire.
- a metal that looks and behaves like gold, but has a melting point similar to steel.
If I decided to allow such creo terram rituals with extra magnitude in unnatural, those would be examples of things I could allow after a discussion with the troupe.
I would definitely rule that a rock that naturally flies to be a highly unnatural rock, and for a spell creating that rock to require muto and auram requisites, since rocks don't have the property of being lighter than air in nature.