Aquamarine is a beautiful blue-green variety of the mineral beryl, and it has the chemical formula Be3Al2(SiO3)6. Here are some of its characteristics:

1. Color: Aquamarine is usually light blue or blue-green in color, although it can sometimes be almost colorless or have a greenish tint.

2. Hardness: Aquamarine has a hardness of 7.5 to 8 on the Mohs scale, which means it is relatively hard and durable.

3. Transparency: Aquamarine is typically transparent to translucent, although some specimens may have inclusions that affect their clarity.

4. Lustre: Aquamarine has a vitreous (glassy) lustre, which means it has a shiny, reflective surface.

5. Origin: Aquamarine is found in various parts of the world, including Brazil, Madagascar, Zambia, Mozambique, Pakistan, and Afghanistan.

Some of the most famous aquamarine specimens include:

1. The Dom Pedro aquamarine, which is the largest faceted aquamarine in the world at 10,363 carats. It was found in Brazil and is now part of the Smithsonian Institution's gem and mineral collection.

2. The Martha Rocha aquamarine, which is a 134-carat stone named after the Brazilian beauty queen who inspired its creation. It was also found in Brazil and is considered one of the finest examples of aquamarine.

3. The Hirsch Aquamarine, a 109-carat pear-shaped aquamarine that was once owned by the Rothschild family. It was sold at auction in 2019 for over $3 million.

4. The Logan Sapphire and Aquamarine Brooch, which is a stunning piece of jewelry that was gifted to the Smithsonian by Mrs. John A. Logan. The aquamarine in the brooch weighs 39.25 carats and is surrounded by diamonds and a large sapphire.

5. The Queen Elizabeth Aquamarine Bracelet, which is a beautiful piece of jewelry that features a large aquamarine surrounded by diamonds. It was given to Queen Elizabeth II as a wedding present in 1947 and is still one of her favorite pieces.