It is a thumbsized, flattened egg shaped oval. It appears to be an white opal of incredible hardness.
In centuries past these stones were the symbols of the Dragon Knights, The Worthies of the Order of Eternal Flames. They were normally worn on the back of their riding gauntlets, but some riders wore them as crests on their jackets or as a necklass stone. A few were mounted into knives and swords. (The Ancesteral Sword of the House of Bolander has such a stone - as they were long supporters of the Order in the earlier age.)
Since the fall of the last age and the five kingdoms, these stones have been scattered… there was no Order left to concentrate on finding them. These stones have found their way into a variety of settings and places. Now they are nothing more than pretty stones. Or so people think.
The Gem is normall “dull”, appearing as an white opal. When being held by one who is Worthy - of the Order of the Eternal Flame - it will brighten, with an internal fire. When held by its “choosen”, those whos destiny they have created, it glows.
The Gem allows the Choosen to be call a Dragon Partner/ Mount. With some time and work, it will allow the Worthy to communicate with the Dragon Partner.
In the days of old, there was an entire range of magic utilizing the stones. According to the stories, the effects include generating a dazzling light to blind foes (temporarily), gently illuminating an area, calling forth a sword of power, allowing super human leaping ability, and healing. Those techniques have been lost, but if someone had a choosen stone, they could learn many of these with time and effort.