Mignone Halls of Gems and Minerals | AMNH (2024)

Star of India

The spectacular Star of India is just over 563 carats, making it the largest gem-quality star sapphire known. It is celebrated for its well-defined star, which is visible on both sides.

City of Gems

Ratnapura, Sri Lanka, known as the “City of Gems,” has been a hub for the gem trade for more than 2,000 years. Early on, nearby miners supplied local Sinhalese traders with famously fine sapphires and rubies.

Those mines have been supplanted by newer sources, so traders today often travel to East Africa and Australia instead. But Sri Lanka is still renowned for its rough sapphires, especially the popular but rare pink-orange padparadscha (“lotus-colored”) sapphire.

Since early history, rubies and sapphires have been given different names, but they are simply different color varieties of the mineral corundum.

Ruby, the red gem variety, results from the addition of chromium to corundum.

DeLong Star Ruby

This magnificent ruby, known for its strong star and unusually large size, comes from Mogok, Myanmar, a famed source of the finest rubies.

The star, or asterism, displayed both here and in the Star of India sapphire, is caused by needle-like inclusions within the gem, an effect best displayed in a rounded cabochon cut.

Redder than Red Rubies

Why do some rubies have such intense color?

Because they also fluoresce. When illuminated by ultraviolet (UV) rays, the chromium in rubies causes them to absorb this invisible light and then emit it as a glowing red.

UV in daylight make fine rubies glow redder than red.In sunlight, rubies appear super red.

Emerald is the intense green variety of the mineral beryl, which comes in many colors.

Typically, emeralds are heavily flawed, with cracks and inclusions of fluids and mineral fragments from the rocks in which they grew. When these flaws resemble branches and leaves within the emerald, they are referred to as jardin, French for “garden.”

The Patricia Emerald

Found in 1920 by Justo Daza, a local miner, the Patricia Emerald is the largest gem-quality emerald reported from the Chivor Mine in Colombia.

Famous for its crystal perfection, vibrant color, and large size (632 carats), the Patricia Emerald is remarkable for having been preserved in its original state and not cut into gems.

Topaz is known for its beautiful colors, good clarity, and potential for large gems. Colors include pale blue, pale green, yellow, sherry orange, pink, and, rarely, red.

Although hard, topaz has one weak plane in its crystal structure, so it must be cut carefully to avoid splitting.

The Brazilian Princess Topaz

In the 1950s, a 75-pound (34 kg) light-blue, gem-quality crystal was discovered in Brazil.

The technology for cutting such a large stone did not exist, so it was put into storage. Twenty years later, the stone was fashioned into what was, at the time, the largest cut gem in the world—the Brazilian Princess, weighing 9.5 pounds (4.5 kg).

Colorless Crystals

Discarded by Brazilian tin miners in the 1950s, colorless and pale blue topaz crystals—less valuable than tin ore—accumulated in piles of debris.

Decades later, the crystals were rescued from dumps when it was discovered that irradiation and heat turned the colorless topaz blue and deepened the color of pale topaz.

Irradiation followed by heat transforms colorless topaz into an attractive blue. This artificial process is essentially identical to the natural process that creates blue topaz, just much faster.

Diamond is the ultimate gemstone, capable of refracting white light into a brilliant rainbow of colors.

Diamond consists of carbon atoms, which form strong bonds that make it the hardest substance on Earth–and everywhere else!

Best Bling

Does this stunning diamond necklace look familiar?

Rihanna wore the 110-carat diamond Organdie necklace designed by Michelle Ong for Carnet on the cover of Essencemagazine in February 2021. Now part of the Museum's permanent collection, the necklace is on view in the Mignone Halls of Gems and Minerals.

A Spectrum of Colorful Diamonds

While people usually think of diamonds as colorless, most are actually yellowish. Some come in “fancy” colors like pink, blue, purple, and red.Only colorless diamonds reflect white light into the full rainbow spectrum.

Abundant in Earth’s crust, quartz is found in many environments.

The gem forms of quartz that occur as crystals can be of various colors or hues, or colorless, as rock crystal.The colors derive from natural radiation, heat, and trace contaminants.

Pinwheels in Amethyst

A typical quartz is a six-sided prism topped by a six-sided pyramid. Alternating pyramid faces have different surface properties and, as a result, two faces next to each other can display different colors.

The result is a three-bladed pinwheel effect in some amethysts.

Crystals Named for Mountains

Cairngorm is a variety of yellow-brown to orange-brown gemstone quartz named after the Cairngorm Mountains of the Scottish Highlands.

For the past three centuries, locals and tourists, including Queen Victoria, have searched the mountains of these crystals by digging or by collecting them from the surface.

Sparkling Green Garnet

Around 1851, brilliant green nodules of demantoid garnets were discovered in the Ural Mountains of Russia.

Rare and highly valued, this gem variety was named after the now obsolete German word for diamond (demant) because of its diamond-like fire.And because of its original source, the green gem was briefly nicknamed the “Uralian emerald.”

Although most gemstones are minerals, some materials considered to be gemstones are organic, meaning they were originally produced by living organisms.

These include jet, amber, coral, and pearls.

A Pearl is Born

A pearl forms when a foreign body lodges in the mantle tissue within the shell of a living mollusk, typically an oyster.

Unable to remove the irritant, the mollusk secretes thin, concentric layers of nacre to coat it, creating a pearl.

Diving for Pearls

Before modern diving gear, pearls were harvested by specialized free divers worldwide.In Japan, ama, or “ocean women” have been gathering pearls for centuries.

The ama appeared in the first collection of Japanese poetry, dated to AD 750. To this day, ama perform diving demonstrations at the Mikimoto Pearl Island Museum in Japan.

Formed from Tree Sap

Amber is fossilized resin, such as sap from conifer trees.

Though hard enough to be drilled and carved, these resins were once sticky and fluid enough to trap insects and other small animals, which can still be found inside some amber gems.

The dazzling colors seen in gem tourmalines depend on the metals present in each gemstone’s crystal structure.

Pink tourmalines contain more manganese, while green crystals include iron, chromium, or vanadium.

The Empress’s Passion

In the late 1800s, California’s San Diego County was the leading source of tourmalines.

The Chinese Dowager Empress Tz’u-Hsi was particularly fond of red and pink tourmalines and had great quantities of them shipped to China.The sought-after gems were then fashioned into jewelry and carved into snuff bottles and buttons.

Extraordinary Elbaite

The Mignone Halls of Gems and Minerals feature a stunning elbaite tourmaline, named the Tarugo, which is one of the largest intact mineral crystals ever found.

Discovered in 1978, the Tarugo comes from a gem pocket in Minas Gerais, a Brazilian state renowned for its mineral wealth. Tourmaline crystals from this pocket are notable for their exceptional quality and cranberry color.