What Are the Rarest and Most Beautiful Gemstones in the World?

These days, it feels like there’s an endless array of gemstones for us to admire and explore. Of course, we're most familiar with popular gemstones like sapphire, emerald, and ruby—but many of the most beautiful and rare gems remain relatively unknown to most people.

Humans from many different cultures have always appreciated gemstones for their beauty and symbolism. It’s not difficult to see why we are drawn to them. In ancient civilizations, rulers were adorned with beautiful gemstones and often buried with them.

Fast forward to today, and you’ll find collector-worthy gemstones fetching sky-high prices at auction. These stones are prized for their rarity and beauty—remarkable natural treasures that remind us just how incredible our planet truly is. Rare gemstones often have high clarity or excellent color, while others produce interesting optical effects–such as color change.

There are five types of gems which we would consider the rarest and most beautiful in the world. Before we reveal what those are, let's review how gemstones are graded. This will help you understand what makes certain gems so rare (and valuable).

Gemstone Grading 101

Colored gemstones are graded on their own unique scale—similar to diamonds, but with some key differences that reflect their distinct characteristics. While most people are familiar with how diamonds are graded, colored gemstones often don’t receive the same level of attention or understanding when it comes to their unique qualities and grading nuances.

To start, color is the biggest grading factor for gems. It’s broken down into three parts: hue, tone, and saturation.

• Hue: This is the basic color you see (like blue in a sapphire or red in a ruby).

• Tone: Describes how light or dark the stone is

• Saturation: Refers to how rich or intense the color appears.

The most valuable colored gemstones usually have vivid, well-balanced hues and bold saturation. But color isn’t the only thing that matters. Just like diamonds, colored gems are also evaluated on their clarity (how many imperfections are visible in the stone), cut (how well the stone is shaped), and carat weight (how small or large it is).

One additional aspect to keep in mind when determining gemstone value is whether the stone has been treated with some kind of enhancement to improve color or clarity. While treatments can make a gem look better, they usually lower its value because the stone is no longer considered completely natural.

Now that we've explained how gems are graded, we present our list of what we consider to be the rarest, most beautiful types of gems in the world.

1. Alexandrite

One of the most well-known rare gemstones, Alexandrite is especially prized for its remarkable ability to change color depending on the lighting. The chromium present in Alexandrite causes the stone to change from an emerald green color in natural daylight to a ruby red or purple color when in incandescent lighting. Alexandrite was originally discovered in 1830 in Russia’s Ural Mountains and was named after the future Russian Tsar Alexander II. Today it is mined in Brazil, Sri Lanka, India, Madagascar, and Zimbabwe. Alexandrite has a hardness of 8.5 on the Mohs scale, making it durable enough for use in jewelry. However, because natural Alexandrites are so rare, they aren’t commonly seen in everyday jewelry pieces. The Smithsonian has a gorgeous 66-carat Alexandrite specimen on display for the public to appreciate.

2. Tanzanite

Discovered in 1967 by the Maasai tribe in Tanzania, Tanzanite was originally thought to be a sapphire. It was given the name Tanzanite by Tiffany & Co. who assisted in making it popular once gemologists confirmed that it was a new type of gemstone. It's currently only mined in the foothills of Mount Kilimanjaro and is one of the world’s most rare gemstones. While it is not considered a color change gemstone, Tanzanite can look blue or purple depending upon the angle of the light source. With a hardness of 6 to 7 on the Mohs scale, this gemstone can be used in jewelry, but care must be taken when wearing it, as it is more susceptible to scratching and other damage.

3. Paraiba Tourmaline

Discovered in the Brazilian state of Paraiba in the 1980s, the Paraiba tourmaline has a distinct blue-green glow that is a result of the copper and manganese present in the gemstone. Today it is mined in Nigeria and Mozambique as well. It has a hardness of 7 to 7.5 on the Mohs scale, which makes it suitable for jewelry–though certainly not the most durable gemstone. Care should be taken when wearing Paraiba tourmaline jewelry—not just due to its delicate nature, but also because of its exceptional rarity and high value. The most famous Paraiba tourmaline specimen is the Ethereal Carolina Divine Paraiba, which is 191.87 carats.

4. Black Opal

Opals are a popular gemstone, though most people are familiar with the classic white variety. However, there are several other types—like the rare and striking black opal—that aren't as commonly seen. Black opal is a variety of Australian opal—Australia produces about 95% of the world’s opals—and is primarily mined in Lightning Ridge, New South Wales, where it was first discovered in the 19th century. Black opals have a dark body tone, which shows off their play of color very well. The name of this gemstone can be a bit misleading, as black opals aren’t truly black. They typically range from dark blue to dark gray, but can appear black due to the striking contrast with their vivid flashes of color—usually red, blue, and green—a phenomenon known as opalescence. Opals have a hardness of 5.5 to 6.5 on the Mohs scale, which makes them delicate and prone to damage if not treated carefully. 

5. Red Beryl

Originally discovered in the Wah Wah Mountains of Utah in the early 1900s, red beryl is incredibly rare. It has a bold red color due to the manganese present in the gemstone. Since it is found in small rough crystals, there are not many larger faceted specimens of red beryl. This gemstone has a hardness of 7.5 to 8 on the Mohs scale, so it is considered fairly durable, but because of how rare and expensive it is, you won’t see much red beryl jewelry available for sale. The Gemological Institute of America has one of the largest faceted red beryl specimens in their collection, weighing 8.0 carats.

Final Thoughts

Rare gemstones are considered rare for good reason, as we've seen—their scarcity and unique optical effects set them apart from more common stones.

If you're captivated by the fiery flashes of a black opal, the color-changing magic of alexandrite, or the vivid glow of a Paraiba tourmaline, each gemstone serves as a stunning reminder of nature's magic. Whether you collect rare gems or simply enjoy learning about them, they offer a fascinating glimpse into just how extraordinary these natural treasures can be. As technology advances and new discoveries are made, who knows what other extraordinary gemstones will be unearthed.