International School of Gemology August 10, 2022

ISG: The Story of Aquamarine

In 1910 a single aquamarine crystal weighing 550,000 carats was found in the Marambaia region of the state of Minas Gerais in Brazil. This find, among many others over the decades, has placed Brazil as the world leader in aquamarine production in both quality and quantity. For many years the world’s largest mining company producing aquamarines was Amsterdam Sauer, led by Jules R. Sauer (RIP) of Sao Paulo, Brazil. I had the honor to work for the Mr. Sauer as gemologist in their retail store on St. Thomas, U.S. Virgin Islands. During this time, I got to experience the finest aquamarines in the world. After founding the Caribbean Gemological Institute, I worked with the Sauers on projects for the next 10 years. Jules wrote an important book: BRAZIL: Paradise of Gemstones, from which several images in this article were scanned, including the banner above. It provides a look at aquamarine qualities that few in the United States jewelry industry get to experience.  Allow me to share what J.R. and his wife Zelda taught me during those amazing years.

Aquamarine crystals form in the vast pegmatite dikes found in Brazil. Here you see a small pegmatite intrusion in host rock from Mason County, Texas. While these intrusions are only a meter or two in width, the Brazilian pegmatites measure in kilometers. These are formed when extremely high pressure and high temperature, mineral-rich water forced its way into the existing rock. As it cooled the minerals in the water, and along the contact zones with the existing rock, joined to form beautiful blue crystals of beryl called aquamarine for their ocean blue colors.

Aquamarines form in long prism-shaped hexagonal crystals in the pegmatite dike. Here you see one of the hexagonal crystals in this pegmatite quartz, purchased for the ISG Student Reference Collection from a Brazilian "garimpeiro" or miner.

Viewed down the top of an aquamarine crystal (or the "C" axis) the hexagonal shape of the aquamarine crystal serves as an important identification tool of the blue gemstone.

Seen here is what is perceived by many U.S. jewelry store sales staff as the classic aquamarine color. In fact, this is considered a commercial quality aquamarine due to this very light blue color. The finest quality aquamarines will rival a fine blue sapphire as seen in the image below. Natural unheated aquamarine will have an intense blue color with greenish overtones. The natural aquamarine will look more like open ocean water than any other, hence the name. Aqua marine = sea water. Jules Sauer’s wife, Zelda, had the largest and most amazing collection of natural, untreated aquamarines in the world.

Below is a scan from Mr. Sauer’s book. I once asked Mr. Sauer why only the light colors of aquamarine were shipped to the United States while the very finest colors were sent to Japan and Europe? His answer I will always remember: “The U.S. jewelers only want low prices; the Japanese and European customers demand the finest qualities”. I was to learn that this is true for many of the amazing gemstones produced by the Brazilian mines. 

Gemological Properties

Source: Numerous places around the world including Brazil, Nigeria and United States.

Chemical: Be3Al2(SiO3)6

Formation: Prismatic crystals

Unusual Properties: None.

Colors: Finest untreated color is a greenish blue. Heated the stone will turn pure blue. Light blue often seen as inexpensive variety of aquamarine on many world markets. Darker blue and natural greenish blue are become rather rare and are expensive.

Wearability: Very good.

Refractive Index: 1.577 – 1.583 and can vary based on iron content.

Birefringence: .005 – .008

Optic Character: U-

Crystal System: Hexagonal

Specific Gravity: 2.67 – 2.75 range

Hardness: 7.5 – 8.0

Transparency: Transparent to translucent.

Spectrum: Weak bands in the 456nm, 427nm and 537nm possible.

Special Identifying Properties and Tests: Anything with above colors in the beryl family will be aquamarine.

Imitations and Created: Many possible. Often confused with blue topaz. Very fine quality hydrothermal aquamarines are on the market. Hydrothermal aquamarine is an easy identification with magnification for a trained gemologist. Below is a hydrothermal aquamarine in 10x and 60x showing classic hydrothermal growth structure.

I hope you enjoyed the Story of Aquamarine. Join us each week for this new educational series on the amazing world of gemstones. If you are interested in the world's most amazing (and affordable) study of gemology and jewelry appraisal, we invite you to review our program by clicking the ISG icon below.

Robert James FGA, GG

President, International School of Gemology

Global Claims Associates

Property and Casualty Adjuster, Texas Department of Insurance #1300433

View this educational page on our website: ISG The Story of Aquamarine

We are adding every week. View additional educational pages on our website:

ISG The Story of Abalone

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