Adamantine dragon

Adamantine dragons, also called adamantite dragons, were a species of planar dragon.

Description
Adamantine dragons had a typical draconic build, but their bodies were relatively small in proportion to their claws, wings, and tail. They ranged in size from wyrmlings to  great wyrms. Adamantine dragons were born with their scales- which looked like silvery metal covered in diamond dust- fully developed. It was said that the light that reflected from their scales in brilliant beams and scintillating rainbows was refreshing to those who could bask in goodness, but painful to the evil. On the head, horns swept back and formed a radiant, crownlike crest.

Trivia
Adamantine dragons were among the planar creatures known to respond to the elven High Magic summoning spell celestial army.