Currently the Heart of the Keep has the following description:
A large golden yellow diaspore. This rectangular stone is as large as a man's palm and cut to highlight it's brilliant sparkling depths. From within those depths is a warm glowing light, much like a fire's flame.
As it is keepstuff, and that is the source of its magics, it doesn't show an aura of enchantment in the way a sorceror would identify it.