Ignium

Mineral that attracts and traps ambient blue quanta. As it does so, it gains an orange/yellow color (extremely similar to glow of sunrise/set) and luminescence. Without energy, it is a pale blue crystal color. Ignium has similar density to iron (8g/cm3).
Exposed to air, it naturally leaks stored energy from outer layers first, resulting in what looks like flame trapped in pale crystal.
Used in synthesis of Arcsteel.

The 6 Phases of Ignium

Ignium has the distinct property of having 6 distinct states (and a volatility limit) from which the first 6 levels of magical charged were derived, hitting its volatility limit at exactly 6 stokes. As layers diffuse magical energy, they regress in state- this is seen in natural ignium deposits where the very edges of deposits consist of phase 0 ignium, transitioning to phase 1 a few inches in, with pockets of phase 2 at the thickest areas, creating the impression of fire trapped in glass. Ignium's internal reflection properties mean that most energy remains within the material, only slightly leaking once a phase-reduced 'layer' is formed (similarly to oxidization). Despite energy levels being continuous values, there is a precise transition point where observed behavior changes.
0- standard 'external' ignium, clear, pale blue
1- standard 'internal' ignium, orangeish and glowing, light levels oscillate/pulse
2- standard 'central internal' ignium, constant orange-yellow light dotted with points of light
3- distinct motes of brighter light swirling internally
4- swirling motes leave trails behind them instead of existing only as points
5- motes branch into fractal patterns, leaving trails of white and orange
6- volatility limit, explosively combusts

These phases were the original calibration point for the Terian unit of energy density known as the stoke.

Distribution

Ignium naturally forms in the corpses of glasswyrms during their 'decomposition' process, hence the massive deposits within the mountains bordering the Molten Desert.
Outside of this, it's relatively rare to see near the surface. Veins of ignium are common at depths of around half a mile to a mile.