How the World’s Largest Aquamarine Gem Came to Be | Smithsonian Voices | National Museum of Natural History

How the World’s Largest Aquamarine Gem Came to Be

For those that examine what occurs when magma and crust collide, igneous rocks like pegmatites are a welcome sight. But as well as to holding clues about Earth’s mineral and geologic processes, pegmatites deposits are identified for holding numerous and richly coloured mineral crystals that may be reduce into spectacular gems. One of the largest — if not greatest — instance is the Dom Pedro Aquamarine.

This roughly 4.6-pound gem was reduce from an enormous 100-pound aquamarine crystal unearthed in the late Nineteen Eighties. Today, it sits in the Smithsonian’s National Museum of Natural History, engaging guests to discover the Hall of Geology, Gems, and Minerals and galvanizing curiosity about the crystals and minerals resting inside Earth’s rocks.

“It doesn’t look like most gems people are used to looking at, like ones in pieces of jewelry. It draws people into the gallery and gives us an opportunity to show how every gem, just like this aquamarine, started out as a mineral crystal that formed in the Earth,” stated Dr. Jeffrey Post, Curator-in-Charge of Gems and Minerals at the museum.

Journey from the middle of the Earth

Although aquamarines are identified for his or her “color of the sea” blueish-green colour, they’re made of the similar mineral, referred to as beryl, as gems like inexperienced emeralds, pink morganites and yellow heliodors. These gems all begin as high-quality beryl crystals. Each gem’s respective colour comes from impurities inside beryl’s mineral composition. For instance, aquamarines are attributable to including two varieties of iron atoms to beryl because it varieties.

“When you grow pure beryl crystals in a lab, they’re colorless. But it turns out Earth is a pretty dirty place to grow crystals, so natural crystals always contain some impurities,” stated Post. “In the case of aquamarine, iron gets trapped in beryl as its growing. Then, light interacts with that iron and gives the aquamarine its color.”

Beryl is often present in pegmatite formations, which happen when sizzling magma pushes from deep in the earth up into the crust and cools right into a granite physique. As the molten rock cools, it crystallizes. How it crystallizes is dependent upon the focus of water current inside the magma.

“As this magma body is cooling, the more water-rich part is the last to crystallize and rises to the top. It becomes like scum on a cooling pot of soup,” stated Post. “And in this water-rich portion, there is also an accumulation of elements, such as boron, beryllium, and lithium that don’t easily fit into the crystal structures of the minerals in the granite.”

When these parts swirl round the prime layer of crystallizing water wealthy magma, they cool and type minerals like beryl. Sometimes, they soak up different leftover atoms too like the iron that turns beryl into aquamarine.

“When everything is finally cooled, you have a pegmatite body composed mostly of large crystals of quartz and feldspars, and they sometimes have cavities. Miners try to locate these cavities, or pockets, and if they are lucky they will have big crystals in them, perhaps of beryl,” stated Post. “That’s how the Dom Pedro aquamarine was found.”

Sculpting with an uncommon medium

The Dom Pedro was present in a Brazilian pegmatite mine and named after Brazil’s first two emperors. The authentic crystal initially weighed over 100 kilos however shattered into three items throughout its excavation. The largest piece, which was roughly 60 kilos, then traveled to the studio of a well-known gem artist in Germany who sculpted it into the obelisk form it has immediately.

“At the bottom of the obelisk, you’ll see a series of parallel vertical lines, which are hollow tubes, imperfections, that formed when the crystal was growing,” stated Post. “The artist decided to leave them in the sculpture because those imperfections are part of the story for this crystal’s formation.”

Once an obelisk gem sculpture, the Dom Pedro was then offered, and later donated by Jane Mitchell and Jeffery Bland to the Smithsonian’s National Gem and Mineral Collection. It now lives 30 ft from the Hope Diamond, greeting museumgoers as they discover the Hall of Geology, Gems and Minerals in-person and virtually.

“For all our gems, we would like individuals to see them and notice that the Earth is a tremendous place, and that science is extra fascinating than they could have thought,” stated Post.

A gem of a group

By learning how crystals, minerals and rocks type, mineral scientists at the National Museum of Natural History are studying extra about the world’s geologic previous and current. For instance, rocks can train researchers what early Earth’s mineral composition might have been, whereas meteorites let scientists analyze minerals in the asteroid belt.

All of these specimens, whether or not on show in the Hall of Geology, Gems and Minerals or saved in museum’s assortment, are cared for by the mineral sciences department.

“Every one of these started out as a mineral that formed in the Earth. Our collection is a great way to show people that story,” stated Post.

Related Stories:
What Antarctic Meteorites Tell Us About Earth’s Origin
Why Scientists Find Snowflakes Cool
Get to Know the Hope Diamond’s Keeper
What an Asteroid Could Tell Us About Ancient Earth
Check Out the Monopoly Board You Wish You Had as a Kid