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What is Natural Aquamarine?
Aquamarine is a precious mineral prized for both its beauty and its distinct chemical and physical properties. It is part of the beryl group, being a variety of blue-green beryl, with the chemical formula Be3Al2(Si6O18).
Physical and Chemical Properties
- Color: Shades of aquamarine range from light blue to blue-green and even blue-green. Its distinctive color is due to the presence of traces of iron in the crystal structure. Depending on the concentration and valence of the iron ions (Fe2+ and Fe3+), the shade can vary.
- Hardness: Aquamarine has a hardness of 7.5 to 8 on the Mohs scale, making it durable enough to be used in jewelry. Its hardness is due to its compact and stable crystalline structure.
- Luster: Aquamarine has a glassy luster and its clarity can vary from translucent to transparent. The most valuable aquamarines are transparent, without visible inclusions.
- Cleavability and Fracture: Aquamarine has an imperfect cleavage and exhibits a conchoidal to irregular fracture. These characteristics influence how it is cut and processed for use in jewelry.
- Crystallization: Aquamarine crystallizes in the hexagonal system, forming long prismatic crystals with distinct facets. These crystals can reach impressive sizes, sometimes weighing several kilograms.
Formation and geological deposits
Aquamarine forms in granitic pegmatites and hydrothermal veins where beryllium-rich solutions cool and crystallize. The conditions necessary for the formation of aquamarine include high temperatures and pressures, as well as the presence of specific chemical elements.
The most famous deposits of aquamarine are found in Brazil, especially in the states of Minas Gerais and Bahia. Other important sources include Madagascar, Nigeria, Pakistan, Russia and the United States (Colorado and Idaho). These deposits are explored for high quality aquamarine crystals.
Optical Properties and Spectroscopy
Aquamarine exhibits an optical phenomenon called pleochroism, where the crystal can show two different colors when viewed from different angles. Usually pleochroic colors are blue and blue-green.
Through spectroscopy, aquamarine shows specific absorption bands in the visible spectrum, due to the iron ions present in its structure. These absorption bands are useful for identifying and differentiating aquamarine from other blue gemstones.
Uses and Processing
-Jewelry: Due to its attractive color and durability, aquamarine is widely used in jewelry, including rings, necklaces, bracelets, and earrings. The most valuable stones are those with an intense blue color, transparent and without visible inclusions.
- Processing: Aquamarine is cut into various shapes and facets to maximize brilliance and highlight color. The most common cuts include the emerald cut, the oval cut, and the round cut.
Historical and Cultural Importance
Aquamarine has a long history, being valued since ancient times. The Romans believed that aquamarine protected sailors at sea and brought good luck on voyages. In Greek mythology, aquamarine was considered the sacred stone of the god Poseidon. In modern tradition, aquamarine is the birthstone for the month of March and is associated with the 19th wedding anniversary.
Care and Maintenance
To maintain the brilliance of aquamarine, it is recommended that it be cleaned regularly with warm water and mild soap, using a soft brush. Avoid exposure to harsh chemicals or sudden temperature changes. It is also good to store aquamarine separately from other gemstones to prevent scratching.