Aquamarine

Aquamarine is the pale blue-to-blue-green variety of beryl, the same mineral species whose green variety is emerald. Where emerald’s color comes from chromium and/or vanadium, aquamarine’s comes from iron — a simpler, more stable coloring agent, which is part of why aquamarine is typically far cleaner and more heavily included-free than emerald at comparable sizes. The name itself, from the Latin for “seawater,” describes the stone’s color better than almost any gem name describes its stone.

Species and variety. Aquamarine is a variety of beryl (Be3Al2Si6O18), sharing beryl’s hexagonal crystal system and its 7.5–8 hardness with emerald, morganite, heliodor, and colorless goshenite — the differences among all of them are purely a matter of trace-element coloring, not underlying chemistry or structure.

Appearance and color range. Natural aquamarine ranges from a very pale, almost colorless blue to a rich, saturated blue-green; much commercial aquamarine is heat-treated to remove a yellowish-green secondary tint and push the color toward pure blue, a stable and widely accepted treatment in the trade. Larger, more richly colored stones are disproportionately valuable, since pale color is common in aquamarine and deep, even blue is not.

Hardness and everyday care. At 7.5–8 on the Mohs scale, aquamarine is a genuinely practical everyday stone — harder than quartz, resistant to scratching from most surfaces, and well suited to rings as well as earrings and pendants. Ultrasonic and steam cleaning are generally safe for untreated, eye-clean stones, though as with any colored gem it is worth checking with a jeweler if a stone has visible inclusions.

Where it is found. Brazil is the best-known commercial source, with significant production also from Nigeria, Madagascar, Pakistan, Zambia, and Mozambique; large, fine Brazilian aquamarine crystals have historically been cut into some of the largest faceted gemstones in the world.

Birthstone role. Aquamarine is a March birthstone in the US 1912, UK 2013, and US current systems (the historical list instead gives March to bloodstone and jasper). It also carries the site’s clearest illustration of how the tropical zodiac derives from the old monthly list: Scorpio begins in October, and the historical October entry is “opal, aquamarine” — but because aquamarine is a variety of the species beryl, and older astrological sources named the stone at the species level, Scorpio’s traditional zodiac stone is recorded as beryl rather than aquamarine specifically. The modern jewelry-trade zodiac list, built the same way from the current monthly list, instead assigns Scorpio to topaz.