Image of assorted precious stones

What are the 4 Types of Precious Stones?

In the field of Gemology, four gemstones in the world have earned the classification of precious stones. These “big four” are diamond, ruby, sapphire, and emerald. In this article, we’ll take a deep dive into each of these gems and highlight interesting facts along the way, courtesy of the Gemological Institute of America (GIA).


A traditional centerpiece of dazzling engagement rings, diamonds are one of nature’s most precious and beautiful creations. Many diamonds come from the earth, about 100 miles beneath the surface, where high temperature and pressure conditions are just right. However, not all diamonds are earth-mined; some are grown in a lab. Lab-grown diamonds are real diamonds, often better quality and lower priced than earth-mined varieties, which are just a few reasons these precious stones are surging in popularity.

Quick facts about diamonds:

  • Recognized today as the birthstone for April
  • Marks the 60th and 75th wedding anniversary
  • Diamond quality is ruled globally by the 4Cs (clarity, color, carat weight, and cut)
  • Composed of a single element: carbon
  • 58 times harder than anything else in nature, making diamonds the hardest mineral on earth
  • Most diamonds were formed more than a billion years ago, deep in the earth’s mantle layers

Learn more about diamond education and custom diamond engagement rings on our blog.


The most valuable type of precious stone in the mineral species, rubies can command the highest per-carat price of any colored stone, including sapphire and emerald. In 2015, a 25.59-carat ruby ring sold for $32.4 million, setting a new record among colored gemstones. The Himalayas, northern Vietnam, and Myanmar’s legendary “Valley of Rubies” are the primary sources of the world’s most renowned ruby gemstones.

Quick facts about rubies:

  • Recognized today as the birthstone for July
  • Marks the 15th and 40th anniversaries
  • Created by the mineral corundum
  • Chromium is the trace element that lends rubies its rich red hue
  • Its strength depends on the amount of chromium present


Blue sapphire is part of the mineral species called corundum. While this precious stone is most known for its pure blue color, sapphire can also range from green-blue to violet-blue. Blue and multiple colored “fancy sapphires” originate in exotic locales, such as Madagascar, Tanzania, Sri Lanka, Myanmar, and Australia. India’s state of Kashmir is home to intensely saturated and velvety sapphires, rare gemstones that set the standard for blue.

Quick facts about sapphires:

  • Recognized today as the birthstone for September
  • Marks the 5th and 45th anniversaries
  • Belongs to the mineral species corundum
  • Comes in every color except red
  • Stars in the world’s most famous engagement ring belonging to Princess Diana and Kate Middleton, Duchess of Cambridge


The emerald is the fourth type of precious stone. Experts estimate that the oldest emeralds originated in South Africa 2.97 million years ago, forming from the green to bluish-green mineral Beryl. According to legend, emeralds contain the power to boost the wearer’s intelligence and wit and were once believed to cure diseases like cholera and malaria. Today, emeralds are beloved for their vibrant spring-green color, evoking soothing, lush gardens and landscapes like Ireland’s “the Emerald Isle.”

Quick facts about emeralds:

  • Recognized today as the birthstone for May
  • Marks the 20th and 35th anniversaries
  • Created by the mineral beryl
  • Cleopatra’s signature gemstone
  • Sale price reached $280,000 per karat in 2011

Beyond these types of precious stones, the world of gemology also includes many other semi-precious gemstones, including opal, pearl, amethyst, onyx, garnet, and many others. To learn more about gemology and the precious stones mentioned in this post, reach out to us online or call (215) 345-6630 today. Led by our GIA-certified graduate gemologist Greg Glemser, we are a family-owned business with a reputation for honesty, integrity, and quality. Request an appointment today.

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