Exploring the deep sea color of 'Santa Maria' aquamarine
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  Exploring the deep sea color of 'Santa Maria' aquamarine

by Guy Borenstein, FGA
July 12, 2012

Aquamarine is a light-toned and slightly-saturated blue to greenish blue variety of beryl. Its name, which means "sea water," is derived from its pleasant marine color. Together with the emerald, aquamarine is among the most popular varieties of the species.

One of the rarest and most expensive varieties of aquamarine are gemstones with a deeply saturated blue color beryl known as "Santa Maria." They are named in honor of Santa Maria de Itabira, which is the site in Brazil where the first such stones were discovered in the 1950s.

The original deposit is almost depleted, and today most of the Santa Maria colors are found in several sub-Saharan countries of Africa, including Mozambique, which in 1991 became the first known African source, Zambia and Tanzania. These gemstones are typically small, with polished gems of more than half a carat being quite rare. Such aquamarine is called "Santa Maria Africana" or "Santa Maria Afrique," to distinguish it from the Brazilian variety.

This month's color analysis focuses on this rare color. For this purpose, an unusually large 9.13-ct. emerald-cut Santa Maria Africana-colored aquamarine gemstone, sourced from Tanzania, was loaned to Gemewizard® by Advanced ACC (http://www.advancedacc.com).

We first photographed the stone under 5500°K fluorescent light, and then analyzed the image using the GemePro Sampler to retrieve the color DNA, the average color and the dominant color components. With the results in hand, we placed the average color within the Gemewizard® color system and compared it to the common aquamarine grades in GemeGrades, which is a grading feature available in GemePrice, to examine its relative intensity.

As can be seen in Figure 1, the analysis showed a dominant medium greenish blue color component (61.65%), offset by darker (19.32%) and lighter (10.23% and 8.81%) tones of the same hue, to provide the medium light, moderately strong, greenish blue average color (Gemewizard code: 20-4-4). The color components' combination and their ratio (where medium greenish blue has the strongest influence and the darker and lighter tones add their tints) show how the remarkable overall color is formed.

When one places the resultant average color in the Gemewizard® color system and GemeGrades and compares it to the common aquamarine grades (Figure 2), one can see that the distance between the common GEM grades and the Santa Maria color is quite significant. As is evident, it falls outside the red border.

The analysis demonstrates clearly that it is the saturation intensity in the medium tones that sets these aquamarine apart from the more common aquamarine color grades. When one considers this characteristic together with fact that the available Santa Maria Africana rough is generally small, as well as non-continuous mining, then one obtains a very good explanation for the significant premium that is added to the price of such a stone.

If you have a magnificent gemstone or colored diamond and would like Gemewizard® to analyze it in one of its next Gem Color Reports, please contact us at info@gemewizard.com.