Rock of Viscid Clay
Rock Of Viscid Clay is a canonical MuTe level 15 spell introduced in ArM5, p. 154.
R: Touch, D: Sun, T: Part
Opinions and Commentary
This spell is moderately useful during stories, but it seems like it would be incredibly useful at a covenant. Repeated casting could let magi quarry stone, dig mines, or even carve tunnels through living rock with great speed -- not to mention easily creating stone containers and tools. A covenant could, for example, operate a quarry as an income source using this spell (or items enchanted with this spell).
It would also be very useful to a Jerbiton magus with in interest in making sculptures.