Riftstone

Riftstone is a crystal substance found throughout the Brass realms.

It is a rare and expensive ingredient valued by mages of all kinds, and also usually serves as a form of currency.

Description:

Riftstone is crystallized Aether, that is to say crystallized arcane energy.
Riftstones are of a blue colour, varying from light or sky blue to a deep azure. The colour is largely determined by the purity of the material, with a deeper shade of blue being more sought after. The purity of the material largely determines not only its utility but also its value.

Riftstone is hard but brittle, akin to glass. The material gives off a slight glow, usually only visible in dim light or complete darkness. It is non-toxic so long as one does not breathe in the dust produced during extraction or processing.

Riftstone is highly stable in its natural state. It can safely be hit or cut, only when its structure is disrupted by a great influx of heat or other kind of energy does the material come undone. When destabilized, rifstone will release pure aether which will rapidly 'bond' with surrounding materials, causing riftstones of lesser purity to bloom from surfaces touched by the light of the flash.
The larger and more pure a sample of riftstone is, the harder it is to 'set off' but the more volatile and wide-reaching the reaction. An impure sample might merely produce a flash of light and a light crust over nearby objects, a moderately pure sample might suddely transmute an inch of materials in a radius around itself and a pure sample might detonate in a flash of light and heat, leaving behind a smoking crater and a room covered in riftstones.

Creation:

Riftstone is created from the remains of deceased Stars.
As these celestial beings die, their bodies fracture into pieces, and those pieces often find their ways onto various realms.

There the riftstones rain down from the skies as shooting stars. Often these are not singular shooting stars but entire small meteor showers.
Upon impact, the riftstone within a shooting star will mix with the soil of the impact zone as the molten riftstone solidifies after its crash. The impact crater of a shooting star will thus usually be covered in a layer of riftstone crystals of varying purity.

If an impact site is covered by dust and soil due to geological activity, it is capable of becoming a subterranean deposit. Ancient meteor showers have created many riftstone deposits on many worlds.
Some scholars speculate the way that riftsones fall from the sky is not natural, that there is an an intent and design behind their origins and behavior. This is disregarded by the scholarly community, as the stars are clearly deceased once their pieces drop unto a world.

Artificial Riftstone: It is possile to artificially grow riftstone. This is a time and resource intensive process and it is very difficult to create high-purity riftstones so it is rarely done. It also risks damage to the surrounding life by draining all aether from the area, a phenomenon referred to as aether depletion.

Use:

Riftstone is an extremely vital resource for sorcerers and other magic practitioners. Due to its inherently orderly nature it is very stable and comparatively easy to work with.

Almost every complex magical working requires it as either a power source, stabilizing agent or both. It is among the most common ingredients for rituals, spells and even many potions.
Pieces of riftstone can be turned into single-use containers for spells that expand a mage's options in combat, Soulstones allowing for the creation of Golems and Magic Items or into arcane foci which make a mage's spells more efficient and reliable.
Some reckless mages even use riftstones in combat to recharge their own spent reserves, though this is not without cost.

Riftstone is so universally used that it is commonly used as a form of currency between different species. Demand always outstrips supply and so you can never truly have too much of it.