Heating Crystals of Haflin Woods

Describe a material in your world that is used as a source of fuel or power. Material
In the Haflan Woods home of the The Elves of the Green Slipper are Crystals referred to as Heating Crystals despite have many uses other than heating. These are found scouted around the woods over ground and under ground. They are a very valuable resource and are mined and or scavenged by many groups and people because of there many uses. Several of there uses including 

1. With either the power of magic or light (usually day light) are lighting device for the settlements of the Elves of the Green Slipper.
2. A heating device which is usually a by product of having it as a light but can also be warmed up by putting it in the hot springs in the Haflan Woods. This was a traditional but probably a necessity back in the days when the Elves moved from the tree tops to the ground and caves.
3. Myth has it that they ae used by magic users to store magic and or information. In addition this is the "gems" that are used in the "transport door" keys.

Properties

Material Characteristics

See through and comes in multiple colures but usually one colour. They reflect light as well as hold tempurature.

Geology & Geography

Haflan Woods

History & Usage

History

First used wh

Discovery

By dwarfs who where mining the area.

Everyday use

Heating and despite barely being sold now it was sold all over the world.

Hazards

Can be blinding when the light reflects through it directly.

Distribution

Trade & Market

It is traded to the the East Continent where there it is used for heating over winter. and to the reptilian species who have moved away from the warm climates. A lot are transported to the capitial of Koywren called Portkoywren as the is a large reptilian population around the capital.

Type

Stone

Common State

Crystal