Gemstones captivate us with their beauty, brilliance, and color—but some stand out not just for their appearance, but for their rarity. When we talk about a gemstone being "rare," we are talking about more than just its availability in the market. True rarity is shaped by a combination of natural and geological factors.
Natural Scarcity
One of the biggest contributors to a gemstone’s rarity is its natural scarcity. Some gemstones simply exist in fewer places on Earth. Limited geographic sources mean that production is finite, and once these deposits are exhausted, the gemstone becomes even rarer.
For instance, Tanzanite is only known to exist in the Merelani Hills near Mount Kilimanjaro in Tanzania. Similarly, Benitoite is exclusively mined in a small area of Central California.
Geological Formation
Gemstones require very specific geological conditions such as extreme pressure, intense heat, rare chemical elements, and millions to billions of years of transformation. The more unique and complex the formation process, the rarer the gemstone tends to be.
For instance, Alexandrite requires both beryllium and chromium to form, but these two elements almost never occur together in nature. Tanzanite is one of the most popular single-source gemstones and is only known to exist in the Merelani Hills of Tanzania. Zircons are some of the oldest minerals on Earth, dating back to the formation of the planet some 4.4 billion years ago.
Mining Challenges
Even if a gemstone is known to exist in a particular part of the world, mining it is not always easy. Many rare gems are found in hard-to-reach areas such as high-altitude regions, deep underground, or in politically unstable territories. These challenges substantially constrain the baseline amount of raw material that can be brought to market.
Paraiba Tourmaline extraction faces a multitude of difficulties as it forms deep underground in small pockets surrounded by extremely hard pegmatites.
Quality
Not all gemstones pulled from the earth are equal. High-quality stones that exhibit the most desirable traits—such as vivid color, exceptional clarity, excellent cut, and significant carat weight—are far rarer than lower-grade material. The larger and cleaner the gem, the less likely it is to occur naturally.
Treatment also plays a major role in rarity. While some treatments like heating and oiling are standard industry practices to enhance a gemstone’s natural color and clarity, others like irradiation and coating are looked down upon as they add artificial colors. However, stones that display their beauty without enhancements are significantly rarer and desired.