Natural Aquamarine

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

- Colour: Shades of aquamarine range from light blue to blue-green and even bluish-green. Its distinctive colour is due to the presence of traces of iron in the crystalline structure. Depending on the concentration and valence of the iron ions (Fe2+ and Fe3+), the hue can vary.

- Hardness: Aquamarine has a hardness of 7.5 to 8 on the Mohs scale, making it durable enough to be used in jewellery. Its hardness is due to its compact and stable crystalline structure.

- Luster: Aquamarine has a vitreous luster and its clarity can vary from translucent to transparent. The most valuable aquamarines are transparent, with no visible inclusions.

- Cleavability and Fracture: Aquamarine has imperfect cleavability 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. Conditions necessary for the formation of aquamarine include high temperatures and pressures, and the presence of specific chemical elements.

The most famous deposits of aquamarine are found in Brazil, particularly 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 being explored for high-quality aquamarine crystals.

Optical Properties and Spectroscopy

Aquamarine exhibits an optical phenomenon called pleochroism, where the crystal can show two different colours when viewed from different angles. Typically, the pleochroic colours are blue and blue-green.

Spectroscopically, 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: Because of its attractive color and durability, aquamarine is widely used in jewelry, including rings, necklaces, bracelets and earrings. The most valuable stones are those with a deep blue, transparent colour and no visible inclusions.

- Processing: Aquamarine is cut into various shapes and facets to maximise its brilliance and bring out its colour. The most common cuts include emerald cut, oval cut and round cut.

Historical and Cultural Importance

Aquamarine has a long history and has been 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 March and is associated with the 19th wedding anniversary.

Care and maintenance

To maintain the lustre of the aquamarine, it is recommended to clean it regularly with warm water and mild soap, using a soft brush. Avoid exposure to harsh chemicals or sudden temperature changes. It is also best to store aquamarine separately from other gemstones to prevent scratches.