This is one big beautiful specimen of North Carolina kyanite in matrix. It also has some micro cinammon garnets and apatite crystals. The kyanite crystals range from clear to royal blue.
Kyanite is a polymorph with two other minerals; andalusite and sillimanite. A polymorph is a mineral that shares the same chemistry but a different crystal structure with another, or other, minerals. Kyanite is an attractive mineral that has a near sapphire like blue color in some especially nice specimens. Kyanite has a unique characteristic in that it has a wide variation in hardness, in the same crystal. The hardness of kyanite is approximately 4.5 when scratched parallel to the long axis of the crystal and approximately 6.5 when scratched perpendicular to or across the long axis. Other minerals usually have variable
hardness on different crystal faces due to a different concentration and oreintation of the atoms in the structure. Diamond is one such mineral, a fact gem cutters take advantage of often.