Design: Anti-Magical Charms [2-1, 4-2, 2-1]
Well...this could have gone better.
Based on your recent success with anchoring crystals to our world with gemstones, your mages have surmised that there must be some link between the crystalline structure of real-world gems and the chaotic nature of magic. As a matter of fact, all of the equations you've come up with (some of which are getting incredibly complex) seem to suggest that's the case - thus emboldening you to attempt to use gemstones to try and capture magic from the surrounding space.
After they finished mopping up what was left of the apprentices, your mages have gone back to the drawing board.
First of all, it seems like only significantly pure crystalline structures (such as diamonds) are even capable of absorbing magical interference. That alone makes the attempt Very Expensive, and the King isn't very happy when you ask to pry the jewels from his crown. Second of all, the spell to encourage gems to soak in the magical essence from the air around it spawns an entirely new realm of algebra your mages refer to as "calculus" - it seems like an entirely useless concept outside of this specific case, but it does explain the drop-off in range the magical absorption goes through. And third of all, absorbing magic has a nasty tendency of making the gems...well, explode. They vibrate suddenly, violently, and without warning shatter into hundreds of fast-moving diamond particles that shred whoever happens to be wearing it. We...aren't exactly sure why.
On the bright side, it's a great way to make diamond powder! Very Expensive