Aquamarine Properties and Characteristics

Last updated on March 2, 2023

The official birthstone for March, aquamarine, is one of nature’s wonders that reminds of transparent waters lapping the white sandy shores of the Caribbean islands. It is a semi-precious gemstone that comes in endless shades of blue and can be a beautiful addition to any jewellery collection.

Aquamarine Origin and Formation

Aquamarine is the light blue to the deep dark blue and greenish-blue variety of the beryl mineral group. The name aquamarine comes from the Latin “aqua”, meaning “water”, and “marina”, meaning “of the sea”, as the colour of this beautiful gemstone is often associated with the ocean and is considered a symbol of tranquillity and peace.

Aquamarine has been used in jewellery for at least 3000 years, with references in Roman, Greek, Egyptian and Sumerian writings.  However, at that time, the gemstone was called “sea-green beryl”. The earliest known use of “aquamarine” in connection with the gem was in Anselmus de Boodt’s gemological work Gemmarum et Lapidum Historia (History of Gems and Stones), published in 1609.

Aquamarine, similar to other beryl family gemstones, forms within igneous rocks (pegmatites) under heat and pressure for hundreds of millions of years. Pegmatites are formed during the final stage of magma crystallisation. When magma under the earth’s crust interacts with mineral-rich rocks, they heat up and form gemstones. Pure beryl is colourless; however, if it interacts with minute quantities of iron, colourless gemstone turns into enchanting blue and produces aquamarine.

Aquamarine is typically found in association with other minerals, such as tourmaline, quartz, feldspar, and mica. It is found worldwide, with the largest deposits in the Minas Gerais mines in Brazil, accounting for around 80% of the world’s supply. Other aquamarine deposits are located in Afghanistan, Canada, China, Finland, India, Kazakhstan, Kenya, Madagascar, Mozambique, Myanmar, Namibia, Nepal, Nigeria, Pakistan, Russia, Sri Lanka, Tajikistan, Ukraine, the USA, Vietnam, Zambia and Zimbabwe.

Aquamarine Colours

Aquamarines can be found in a range of colours, from pale and light blue to deep blue, greenish-blue and green-blue, and the exact colour of the gemstone depends on several factors, including the trace elements present in the crystal and the way the gem is cut. The presence of iron in the crystal structure can cause a greenish tint, while the presence of chromium can produce a more yellowish-green colour.

In general, the purer and more intense the blue colour, the more valuable the stone, meaning dark blue and slightly greenish-blue gems, sometimes referred to as “seafoam” or “mint” aquamarines, are the most valued. Another important factor is the evenness of the colour, which should be consistent throughout the stone with no visible colour zoning.

One particularly rare and valuable type of aquamarine is known as “Santa Maria” aquamarine, named after the location in Brazil where it was first discovered. Santa Maria aquamarine is known for its intense blue colour, caused by a high concentration of iron in the crystal. Today the term “Santa Maria” no longer refers to the origin as most of the Santa Maria de Itabira mines have been exhausted. Instead, it refers to aquamarines featuring similar colours to those originally mined in Santa Maria de Itabira. Another expensive vibrant blue aquamarine is the Double Blue, recently discovered and mined in Madagascar.

Aquamarine is a pleochroic gem, meaning it can change colour dramatically when viewed from different angles. It is visible in deeply coloured stones where the colour can alter from deep blue to almost colourless.

Most of the aquamarine available on the market is heat-treated to give it more of pure blue colour, with naturally occurring blue gemstones being more valuable.

Aquamarine Clarity and Cut

Part of the aquamarine charm is its high clarity. Almost all aquamarines available on the market are eye-clean, meaning they are free of inclusions and blemishes, making them a popular choice for faceted gemstones.

The clarity of an aquamarine can range from eye clean, meaning no visible inclusions when viewed with the naked eye, to heavily included, which can significantly impact the stone’s appearance and value. Inclusions can include tiny crystals, veils, and fingerprints, and can sometimes give the stone a unique and interesting appearance. The gems with visible inclusions are often cut into cabochons, beads or fancy carvings. If crystals contain enough liquid-filled inclusions, they are cut into cabochons to show a cat’s eye effect.

In general, aquamarines can be cut into almost any shape; however, they are often fashioned into round, oval and emerald cuts. Aquamarine can also be cut into a variety of freeform shapes, which are used for all types of designer jewellery, as well as one-of-a-kind ornamental objects.

Fashioned aquamarines often have to be quite large (5 carats >) to show dark, intense colour. However, smaller gems from Nigeria, Madagascar and Mozambique are known for their intense colour in sizes under 5 carats. This is the reason why smaller top-colour aquamarines may sell for more per carat than larger stones of the same colour.

Aquamarine Care and Cleaning

Aquamarine is a durable semi-precious gemstone, 7.5 to 8 on the Mohs hardness scale, meaning it is scratch resistant. However, it is always recommended to remove your aquamarine jewellery before household cleaning since this gem is sensitive to chemicals such as ammonia, alcohol and other acids.

Always remember that aquamarine is sensitive to direct sunlight. If exposed to the sun for a too long period, the colour of the gem can significantly fade, and this cannot be reversed. The same is true for prolonged exposure to heat.

To clean aquamarine at home, use mild dishwashing soap liquid and warm water. Carefully place your gemstones in the liquid and soak them for about 10 – 15 minutes. This will help to loosen any dirt. After the soaking, use a soft toothbrush to remove the dirt. Next, rinse out your piece of jewellery with clean water and dry it with a soft and lint-free cloth. Ultrasonic cleaners are not generally recommended. Steam cleaners should never be used to clean aquamarine, as this gemstone should not be subjected to high temperatures.

When storing aquamarine jewellery, keep it separated from other softer gemstones to protect them from being scratched. Similarly, you will want to protect your aquamarines from harder gemstones such as diamonds, meaning it is a good idea to store aquamarine in individual cloth jewellery bags.

Aquamarine Properties

Featured image: lhmfoto / Shutterstock