Glimglass

Glimglass, sometimes simply 'glim' is a curious substance and perhaps the most important to the function of our world. Coal might be able to work machines and heat houses, and oil might be able to keep a house sufficiently illuminated, neither compares to glimglass nor does anything else.
Harvested from the earth and cut into blocks and faceted gem-shapes, glimglass provides heat and light in copious amounts and keeps cities and towns from losing each other in the dark. Each lamp you see, from street to held, to home, likely has a shaped glim inside shining like the old legends say the stars used to.
The fuel source can produce heat enough to live by, light enough to read by, and colors enough to be left joyful, and all of those comfortably. 
Raw glim comes in most colors, and the refinement process can reach any color that can't be found naturally. The color is important as well, as there is no discernable difference of substance between the colors and it is the determining factor for the amount of heat and light that the lit glim can produce. Some colors, like the deepest blues and the and the starkest whites (those naturally occurring) can get warm enough to redden metal and have been used to keep a blacksmith's forge ready for operation for weeks on end, with fuel only being occasionally added.
Through the process of refinement and cutting, such facets can be controlled to a degree. The heat likely cannot be removed from the equation completely as with the light, but colors like blue glim can be made to produce a soothing light over their searing heat within the foundries of the glimworks.

Properties

Material Characteristics

Looks and feels like colored glass, even in it's tougher, unrefined form. Dropping it even produces the sound one would expect from dropping a glass brick of identical size and shape.

Physical & Chemical Properties

A glim produces both light and heat in some measurement, depending on it's natural color. It can be passively warm or hot. A small twinkle in the dark or a blazing beacon. 
That being said, naturally occurring levels are often on the low end.

Life & Expiration

On it's own, glim doesn't seem to have any sort of end to it's lifespan. However, once it is refined it can burn out over a length of time. 
The exact measurement of time has many factors, from the base color itself to the color it was made into, the quality of the refining and the skill of the refiners, the region that the glim was harvested from, etc.

Distribution

Law & Regulation

At times, glimglass may be rationed by the powers that be in times of war or crisis, but overall there is little regulation on the distribution of the substance in any form. 
The only laws regarding it the immediately come to mind, other than common nuisance laws, is the laws in place to prevent counterfeiting glim or trying to stretch ones supply of raw glim by mixing in actual glass.

Type

Ceramic

Odor

Smokey-ozone, like the aftermath of a lightning strike

Taste

None

Color

Myriad

Boiling / Condensation Point

Varies

Melting / Freezing Point

Varies