Uses of Jet as an arcane material

Jet is transparent to arcane eminations, and can be shaped into a lense by which the perception of magic (via the spell "detect magic") can be focused to percieve finer detail.
Proffesor Yazdani was sitting at his desk one day, evaluating student projects from the second year enchantment students. HIs desk is typically littered with doo dads and trinkets and bits of interesting rocks. One such item was a small three-sided rod. He had bought it at the gems and mineral market, intending to use it as a paper-weight. It was about 3" long and each side of the triangle was about 3/4".
The day wore on, as it does, and soon his office was resonably dark; Yazdani realized he'd have to wrap up his evaluations. But as he cast "detect magic" for the last time, he noticed something strange. The paper in front of the rod was lit by a partial ocatrain rainbow. He lifted the jet rod, and the rainbow dissappeared. Putting it down again, he realized that the aura produced by "detect magic" was being split and projected on to the paper - just as light is split into a rainbow by a prism.
I am sorry to say that the second year enchantments class had to wait much longer thsn expected for their final project reviews. Yazdani spent the next four weeks experimenting with jet and related coal and even diamonds before publishing his seminal paper: "The Optics of Magic: the Use of Jet and Diamonds to Focus Magical Item Auras."
Today, many wizards have a set of jet specticles they use for percieving magic using the simple divination spell "detect magic." Using priciples borrowed from mundane optics, these lenses allow the wearer to see distict ocatrine color bands in the aura projected by magic. This may seem inconsequential, as we already can use the spell to see the aura. But ongoing research is turning up some interesting twists. Some materials traditionally used for enchanting actually seem to absorb part of the spectrum, as colored glass absorbs part of the visible light spectrum. Other materials, such as a thin sheet of lead or an inch of common metal, are completly opaque. Gold is particularily odd, as prolonged exposure to magic seems to imbue the gold with a faint aura, even when the material iteslf is not enchanted.
In fact, the use of jet specticals, and diamond lenses in jewler's loops, is providing some very interesting avenues of research.