Synthetic Crystals

Mage Made Minerals

As the name implies, these crystals are all artificially made, specifically by mages, casting construction. Most often in combination with deconstruction, because many of the components used for these kinds of crystals don't naturally form in their pure state but are locked in forms that make them unusable, and therefore they need to be deconstructed first.
For all of these crystals, the general rule is that ambient environment will not enter or flow through the crystal by themselves, they need to be channeled through by any magic user.

Focusing Crystal

These crystals are used in conduits, they help focus magical spells, and they are designed to conduct the magical energies without altering them or interacting with them too much.
They are made from silicon, which is a common component of most rocks, and infused with magic, to stabilize it, if purified silicon were to interact with the environment naturally, it would turn into regular quartz, the magical infusion prevents this.
When made for conduits, which is their most common purpose, they are often made as small as possible, to increase accuracy, and reduce energy loss due to the surface area of the crystal. They will also wear over time, the better they are made, the longer they will last, but inevitably, the strain of spells being cast through them will cause them to break.
These crystals are relatively easy to make but do require some time to perfect them. If they are not made in a properly cut way, that being with uneven cuts, they will be less effective.

Detection Crystal

These crystals are used to detect magical energies, they are useful for practicing the handling of different magical energies, but more so, to detect the contagion. But beware, when trying to detect contagion, channel the energy through the detection crystal without letting it enter your own body, because it's negative effects will set in on contact, even if you don't cast any spells with it.
These crystals are made from corundum, which is aluminum, which is a component of alum, combined with some atmospheric gasses, then it is infused with magnesium.
Magnesium is a component of magnesia, which can be obtained by deconstruction. The processing of alum into aluminum is an extremely difficult process, only doable for mages.
These crystals, will shine brightly with the color of whatever energy you choose to channel through them, when contaminated energy is channeled through, they will pulsate a deep purple.

Purification Crystal

These crystals are used to purify magical energy, making them safe to use, however, these crystals are rare and hard to make, they cannot be used to detect contaminants by themselves, and they will absorb any unwanted component much better when the mage consciously leaves them in the crystal while channeling energy through it.
They are made from pure carbon, the outside needs to be smooth and hard, but the inside needs to have as much surface area as possible. the bigger the crystal, and the more surface area it has, the more contaminants it is capable of holding.
While the composition of these crystals is fairly simple, they are very hard to make properly, most crystals will end up not removing all contaminants, or leaking them back out. Properly made purification crystals are a clear matt black, they should remove ninety-nine percent of contaminants, and store them indefinitely.
When a crystal is full, it will no longer work as a filter, and this crystal is now useless, however, the contagion within it is a much-desired resource both among scholars, wishing to research it, and taint sniffers, looking for their next high.

Combustion Crystal

There exists a process, in which mages are capable of producing a type of crystal from thin air, and a little bit of water, using only construction, that will explode in the most violent of manner, these crystals are quite unstable, and detonate in any number of circumstances, such as the sun shining on them too much, or simply being dropped on the ground too hard.
These crystals are extremely rare, and the process in which they are made is akin to legend, a knowledge lost to history, and mth promises that those who would uncover the secrets of this ancient technique, would be capable of leveling entire cities, given enough of these crystals.

Related Articles:

Read about construction, and deconstruction:

Read about the Contagion:

Synthetics

The creation of synthetic crystals is a fine art, most will at least attempt to learn how to do it, as it is a lucrative business, but most inevitably lack the talent reserved for the most skilled of construction mages. That, combined with the rarity of mages in general, makes all of these crystals quite expensive.