What Is Aquamarine? A Close Cousin of Emerald

Aquamarine is a blue-to-green variety of beryl (beryllium aluminum silicate) — the same mineral species as emerald, differing only in which trace element does the coloring.

Aquamarine vs. Emerald

Emerald gets its saturated green from chromium or vanadium impurities; aquamarine's blue comes from iron, specifically the ratio of Fe²⁺ to Fe³⁺ ions within the crystal structure. Both form in similar geological settings (pegmatites and certain metamorphic environments), but emerald typically forms with far more natural inclusions — described in the trade as jardin, French for "garden" — while aquamarine tends to grow with fewer inclusions, allowing larger clean crystals and larger cut stones than emerald typically permits.

Why Almost All Aquamarine Is Heat-Treated

Rough aquamarine often has a yellowish or greenish undertone alongside its blue, from the mix of iron oxidation states present. Heat treatment (generally in the 375–450°C range) shifts the iron toward the Fe²⁺ state responsible for pure blue, removing the yellow-green tint permanently and stably. This treatment is so standard and so undetectable without specialized lab equipment that essentially all commercial aquamarine on the market has been heat-treated — untreated aquamarine exists but isn't a meaningfully marketed category the way untreated turquoise is.

How It's Graded

Aquamarine is valued primarily on color saturation — deeper, more saturated blue (sometimes called "Santa Maria" blue, after a historic Brazilian deposit known for exceptional color) commands significantly more than pale material, along with the usual clarity and cut considerations common to colored gemstones.

Where It's Mined

Brazil is the largest and most historically significant source. Nigeria and Madagascar are major current producers; Pakistan's high-altitude Skardu region produces well-regarded material as well.

Quick Facts

Mineral family: beryl (same species as emerald) — Hardness: 7.5–8 on the Mohs scale — Color cause: iron impurities — Nearly always heat-treated — Birthstone for March — Major sources: Brazil, Nigeria, Madagascar.