Transparent crystals so clear they are only barely distinguishable from the air that surrounds them. As such Temperature crystals are frequently imbedded into some kind of protective housing both to make sure they don’t end up lost and to prevent them from causing too much damage. During transport or uses where they are frequently moved this housing tends to be made of sub 1 ring glyphing stones however temperature crystals in permanent locations do tend to find themselves in metallic housings. Temperature crystals are highly sensitive to changes in light levels, hence why those that find themselves under circumstances of rapidly changing light levels are contained within glyphing stones, where their illumination can be regulated. The darker the environment the temperature stone is in, the hotter the temperature crystal gets. For this reason temperature crystals are typically put in highly visible locations and in the case of metal shielded ones, with as little housing as possible. There is little risk of someone trying to steal temperature crystals as the act of taking an unshielded crystal and putting it in your pocket is enough for it to radiate enough heat to give second and even third degree burns.
Normal Use: Many temperature crystals are used in cooking, there are some in many types of camping supplies and few houses use temperature crystals to emulate a heating system, however this has to be carefully regulated to prevent the house from burning down. Temprature crystals are almost a necessity in the Lands of the Cold not only for the obvious reason that it’s cold and many species need heat to live but in the fact that temperature crystals are needed to melt down ice into water both for the purposes of drinking and for the purposes of creating things out of ice (the land’s of the cold using ice where other communities would use wood, stone and metal).
Relic examples: Glass weavers are spear like weapons used exclusively in the seas of historia. Only instead of a blade or point has a brush like head which hides a temperature crystal in it. While it can be used to poke and burn glass weavers are more commonly used to sweep sand up off the floor and turn it into glass structures to simultaneously defend and attack depending on the sweeping action used.