Allison and Roberto Mignone Halls of Gems and Minerals
The Mignone Halls of Gems and Minerals tell the fascinating story of how the vast diversity of mineral species arose on our planet, how scientists classify and study them, and how we use them for personal adornment, tools, and technology. The galleries feature more than 5,000 specimens from 98 countries.
These halls are included with any admission.
Signature Mineral Specimens
Sterling Hill Slab
This slab of rock from Sterling Hill Mine in Ogdensburg, New Jersey, showcases some of the 90 spectacular fluorescent minerals species found at Sterling Hill and neighboring Franklin deposit.
This stunning 838-lb (380-kg) specimen is one of the largest stibnites on public display in the world. The bladelike crystals grew to such lengths because they formed in a large underground cavity. Find out more about how minerals form in hydrothermal environments.
This 3,000-lb (1,400-kg) block of igneous labradorite is extraordinary not only because of its spectacular iridescence, but also because of its uncommonly large crystals. Learn more about igneous environments like the one where this mineral formed.
One of two giant amethyst geodes displayed in this hall, this specimen features quartz that formed nearly 135 million years ago in a hydrothermal process, which requires hot water to transport dissolved minerals.
This massive block features vibrant blue azurite and green malachite, both copper ore minerals. It was collected in 1891 from Bisbee, Arizona, a vital source of U.S. copper, and arrived at the Museum in 1894. It formed through a weathering process.
This 5-foot (1.5 m) crystal section is one of the largest beryl crystals in any museum in the world. It comes from a pegmatite, a special kind of igneous rock that produces large crystals, the final product of some cooling magmas.
This slice of petrified dawn redwood from central Oregon turned to stone after being buried by volcanic ash. The volcanic debris enriched the groundwater around it with silica, which mineralized the wood.
The giant garnets in this 14,500-lb (6,577-kg) slab formed more than 1 billion years ago, when the original rock was buried 16 miles underground in upstate New York, and transformed by heat and pressure. Find out more about how minerals form in metamorphic environments.
The Sterling Hill Mine operated between 1850 and 1986, producing 11 million tons of unusually rich zinc ore. It wasn’t until the early 1900s that the mine’s true colors shone, when sparks from a flickering electric lamp revealed the fluorescent minerals in the ore’s body.
Exposure to ultraviolet (UV) light excites electrons in the minerals. When this high energy is released, for some minerals, it is released as light in the lower-energy visible spectrum: fluorescence. Under long-wave UV, calcite appears pale pink and the willemite is pale green.
Short and Sweet
Short-wave UV light travels at a higher frequency and energy than longwave UV. Because of this difference, the color and intensity of light released during fluorescence may also change. Calcite in the slab fluoresces bright red-orange and willemite glows intense green.
The large stibnite crystals are made up of tiny building blocks called unit cells, in which atoms and sulfur combine in a regular arrangement. Unit cells repeat in a 3D pattern to form a crystal.
Stibnite (Sb2S3), a compound of the elements antimony and sulfur, occasionally forms nests of delicate, swordlike crystals, but examples this large and intricate are exceedingly rare.
Hydrothermal processes like the one that formed this stibnite require hot water, which dissolves mineral components and transports them along fractures and through porous rocks.
This ancient stibnite formed in southeastern China, the site of extensive volcanic activity some 130 million years ago.
This mineral’s iridescence comes from light scattering from submicroscopic layers within individual labradorite crystals.
This specimen boasts very large crystals—some of them measure up to a yard (1 meter) long!
Made in Madagascar
This specimen comes from a huge igneous intrusion that formed when tectonic plates collided between 630 million and 550 million years ago.
Most objects absorb some colors from white light and reflect the color you see. The surface of this specimen absorbs most of the colors of light, so it looks gray—until you’re at the proper angle to see the colorful light scatter.
Purple For Now
It took millions of years for these crystals to turn from colorless quart to purple amethyst quartz. Natural, high-energy radiation from the hosting rocks caused the color, which intensified with time and exposure.
Lots of Layers
In addition to purple amethyst quartz, this geode has a layered rim of white, gray, and brown chalcedony, a variety of quartz with ultra small crystals.
This geode weighs around 11,000 pounds (5,000 kg), more than its sibling specimen—which is taller but lighter, at 9,040 pounds (4,100 kg).
Weak acids in rain and groundwater dissolve carbonate minerals such as calcite, the primary material in limestone rock that hosted this block. Over millions of years, dissolution of limestone bedrock can form dramatic caves.
Crystals of bright green malachite and deep blue azurite can be seen in this block’s cavities. These formed when acidic, copper-rich fluids flowed through cracks in the original limestone and deposited azurite, malachite, and some iron oxides.
This roughly 7,200-lb (3,300 kg) block contains around 3,400 pounds (1,500 kg) of copper—enough to wire 17 single-family homes with electricity.
Sing a Song
For years, this spectacular specimen made high-pitched sounds when the humidity changed with the seasons, as the porous stone absorbed and released moisture from the air. Now that it is in a controlled environment, it has stopped singing.
In addition to forming giant crystals, many pegmatites have minerals that concentrate rare elements, like beryllium (Be) in beryl.
Beryl is an important source of beryllium, which is light and stiff with a relatively high melting point. These properties make it useful in aerospace materials, including in mirrors for the James Webb Space Telescope.
One of Ten
This big beryl comes from the Bumpus Quarry in Albany, Maine. It was one of 10 enormous beryls that measured up to 19 feet (5.8 m) long and 4 feet (1.2 m) across.
Preserved by Volcanoes
When this dawn redwood was buried, an early volcanic arc was forming as an ocean tectonic plate subducted under western North America. Volcanoes erupted violently and deposited thick layers of volcanic ash, burying the forest.
This dawn redwood lived about 35 million years ago in the present-day Cascade Mountains. Earth’s climate was warmer and wetter then, and the range of the dawn redwood extended above the Arctic Circle.
Extinct in the USA
Today, native dawn redwoods grow only in a few forests in China. It’s likely their extinction in North America had many causes, including a change in climate change, ecological shifts, and modifications in global topography.
Count the Rings
The rings of this fossil dawn redwood were preserved during fossilization, so that you can count them to estimate how long it lived. Though some rings have become distorted over millions of years, experts have counted up to 884 individual bands.
Made in New York
This towering slab studded with garnets of up to 1 foot across comes from New York’s Gore Mountain in the Adirondack Mountains.
These garnets are unusual because they are cracked along many parallel planes—which makes them perfect as an abrasive, like sandpaper.
The garnets resulted when rock transformed at pressure 8,000 times greater than atmospheric pressure (and at about 1500° F (815° C).
During metamorphic reactions that formed these garnets, elements moved between solid minerals via chemical diffusion.
Hall of Gems
More than 2,000 gems, carvings, and jewelry pieces are on view. Explore a few below.
Sapphire is a gem variety of the mineral corundum. Beyond the classic blue color, sapphires range from colorless to orange to green to violet, but not red–red corundum is ruby.
No cleavage, generally tough
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.
No cleavage, generally tough
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.”
Beryllium aluminum silicate
No cleavage, moderate durability
Tends to contain inclusions
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.
Aluminum silicate fluoride-hydroxide
Perfect cleavage plane in one direction
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).
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!
10 - hardest substance known
Perfect cleavage planes in four directions
High dispersion, yielding fire and superb brilliance
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 Essence magazine 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.
Garnets occur in a variety of colors. But the most common garnets, pyrope and almandine, are generally red, and the name ”garnet” derives from the Latin granatum, meaning pomegranates.
Pyrope, Almandine, Spessartine, Grossular, and Andradite
No cleavage, good durability
Rhodolite, demantoid, tsavorite, hessonite, topazolite, malaia, gooseberry
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.
No cleavage, can be fragile
Elbaite, dravite, uvite, liddicoatite
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.
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.
See more than 40 spectacular green jewels in the new exhibition Garden of Green: Exquisite Jewelry from the Collection of Van Cleef & Arpels, now open in the Melissa and Keith Meister Gallery.
See this dazzling suite of 240 diamonds representing every variety of fancy colored diamond in existence, known as the Butterfly of Peace, on view in the Mignone Halls of Gems and Minerals.
The Museum gratefully acknowledges Allison and Roberto Mignone for their leadership support of the redesigned Halls of Gems and Minerals.
Generous support has been provided by Melissa and Keith Meister, the Arthur Ross Foundation, Kenneth C. Griffin, and David Yurman.
Additional support has been provided by the John & Amy Griffin Foundation and the City of New York.