Some birthstone designations have been contested, revised, or complicated by alternatives. February's hasn't. Amethyst has held the month's singular designation since 1912 without revision.
Myth & Meaning
Jewelry is full of encoded meaning, but the eternity band is unusually literal about it. The continuous stone circle has signified infinite love and unbroken devotion for centuries, a design that says exactly one thing and refuses to be misread.
Stone Story
Amethyst jewelry spans a broad color range, and the grade makes a visible difference. Pale lavender through mid-violet are the accessible tiers, and the most prized stones show a deep, even purple with rose and red secondary hues. The trade calls that top color grade Siberian amethyst, which is a designation based on quality, not origin.