Amethyst

Amethyst is the purple variety of quartz. It is also one of the rare places in birthstone tradition where four systems agree on the same stone for the same month: February. Those are the historical list, the 1912 US standard, the 2013 UK list, and the current US list.

The historical list also allows hyacinth (zircon) or pearl as February alternatives. However, amethyst is the constant across all four.

Species and variety. Amethyst is a macrocrystalline (single large-crystal) variety of quartz, SiO2, in the same family as citrine, rock crystal, and smoky quartz. All of these differ only in trace impurities and irradiation history, not in underlying chemistry or crystal structure. Specifically, its purple color comes from trace iron substituting into the quartz lattice. Natural background radiation over geological time converts that iron into color centers, which absorb light and produce the characteristic violet-to-purple hue.

Appearance and color range. Amethyst ranges from pale lilac to deep, saturated purple with reddish or bluish secondary tones. The deepest, most even color is generally the most valued.

Heat treatment can lighten amethyst or shift it toward yellow or orange. For example, the great majority of commercial citrine is produced this way, by heating amethyst or smoky quartz. That is worth knowing, since it means “natural citrine” and “heated amethyst” can describe the same physical process on the same rough material.

Hardness and everyday care. At 7 on the Mohs scale, amethyst is durable enough for daily wear in rings, earrings, and bracelets. It holds up well against household dust and most surfaces it might brush against. It is not immune to scratches from harder materials, such as sand or other gems.

Like most colored quartz, its color can also fade with prolonged intense light exposure. As a result, it’s best to avoid leaving amethyst jewelry in direct sun for extended periods.

Where it is found. Brazil and Uruguay are the largest commercial sources, often mined from geode-lined basalt cavities that can be spectacular in their own right. Additionally, Zambia, South Korea, Russia, and Sri Lanka produce gem-quality material.

Birthstone role. Beyond its unusually unanimous status as the February stone, amethyst is also the traditional tropical-zodiac stone for Pisces. That is not a coincidence. The tropical-zodiac list is derived by keying each sign to the historical monthly stone for the calendar month it begins in.

Pisces begins on February 19, so it inherits February’s amethyst. In contrast, the modern jewelry-trade zodiac list, built the same way but from the current monthly list, assigns Pisces to aquamarine instead.