Stibnite was and continues to be the primary ore of antimony. Stibnite forms some of the most outstanding natural crystals that exist, in way of sharpness, luster, and size. It can form in groups of huge metallic lustered crystals that are elegantly crafted and exceptionally shiny. In long and slender prismatic crystals, often densely grouped at different angles or in starburst aggregates. Single crystals, which can be quite large in a few localities, can resemble swords. Terminated crystals have pyramidal or flattened, slightly pointed terminations. May also be in thin fragile needles, reticulated, radiating, grainy, massive, encrusting, reticulated, and capillary. Crystals are deeply striated vertically, and may also be bent, curved, or warped. The color is metallic silver-gray.