silicates
Aquamarine
Be3Al2Si6O18
- Crystal system
- hexagonal
- Hardness
- 7.5–8 on the Mohs scale
- Lustre
- vitreous
- Colour
- Pale blue to blue-green
- Where it forms
- In granite pegmatites, often as large clean crystals — aquamarine forms some of the largest gem-quality crystals of anything.
- Chiefly from
- Minas Gerais, BrazilPakistanNigeriaMadagascar
Why it is that colour
Iron. Iron in one oxidation state gives blue, in another gives yellow, and most rough is a mixture that reads greenish. Nearly all commercial aquamarine has been heated to about 400 degrees to convert the yellow component and leave pure blue.
Safety
Safe to handle; beryllium dust from cutting is the hazard, as with all beryl.
Where it comes from
Brazil is the traditional source; Nigerian and Pakistani material is now significant. Pakistani and Afghan mining is largely small-scale and hazardous, worked at altitude with explosives and little equipment.
Historical use
Used for intaglios in the Roman period and popular ever since. The Dom Pedro aquamarine, cut from a Brazilian crystal in 1992 and standing thirty-five centimetres tall, is in the Smithsonian and is the largest cut aquamarine known.
Recorded as history and attributed where possible. That a stone was used for something establishes that people used it, not that it worked.
What is attributed to it, and since when
The name is Latin, water of the sea, and Roman sources associate it with sailors and safe passage — one of the few sea associations that is genuinely ancient rather than reconstructed. Modern meanings around communication and calm are twentieth-century.
Described, not endorsed. Dating a claim is not the same as assessing it — but an association that first appears in a book published in 1985 is not an ancient inheritance, whatever the label says. A sincere account of feeling better is compatible with the stone doing nothing — see the placebo effect.
Sold as this, but not
Worth knowing
Almost every aquamarine you will ever see has been heated. The treatment is permanent, undetectable and universal, and it is disclosed as standard practice in the gem trade because everyone assumes it. Untreated greenish material is now sold at a premium to collectors who want the stone as it came out of the ground.
That is a reasonable arrangement, and it is worth contrasting with the citrine situation. Both are heat treatments of a common mineral. The difference is that one market treats disclosure as routine and the other does not.
Identity checked against IMA-CNMNC master list, June 2025.