Antimony is light gray with a metallic luster and in some cases is nearly indistinguishable from arsenic. There is some conjecture on whether it was one of the stones included in the breastplates of Semitic high priests, but archeologists are sure it was known and used in Biblical times as a medicine and cosmetic.
Tenacity in all areas of interest is enhanced by antimony. It dispels opposition so long as your goal is not detrimental to others, and encourages and stimulates access to instinctive knowledge.