In the fascinating world of gemstones, hardness is often a key consideration, especially for pieces that will be worn frequently and need to withstand the test of time. The hardness of a gemstone is measured on the Mohs scale, which assesses the ability of a gem to resist scratches and abrasions. This scale is pivotal for gemologists and jewellery enthusiasts alike. Here, we spotlight the top 7 hardest gemstones, delving into their color range, crystal structures, and where they rank in terms of hardness.
1. Diamond
- Hardness: 10 on the Mohs scale
- Colors Available: Colorless, yellow, brown, and sometimes in fancy colors including blue, green, pink, and red.
- Crystal Structure: Cubic
The undisputed champion of hardness, diamonds are not only the hardest known natural substance on Earth but are also renowned for their sparkling brilliance. Their cubic crystal structure contributes to their incredible strength and is also the reason behind their unique way of refracting light.
2. Moissanite
- Hardness: 9.25 to 9.5 on the Mohs scale
- Colors Available: Mostly colorless but can display yellow, green, and gray hues.
- Crystal Structure: Hexagonal
Moissanite is a naturally occurring silicon carbide and is now primarily lab-grown due to its rarity in nature. Its hardness is close to that of diamonds, which makes it an excellent choice for jewelry that can endure daily exposure.
3. Sapphire
- Hardness: 9 on the Mohs scale
- Colors Available: Blue is the classic color, but it can also be pink, yellow, orange, green, and clear.
- Crystal Structure: Trigonal
A variety of the mineral corundum, sapphires are cherished for their deep blues as well as their fancy colors. The strength of sapphires makes them a top pick for engagement rings and other high-wear jewellery.
4. Ruby
- Hardness: 9 on the Mohs scale
- Colors Available: Ranges from pinkish-red to a deep, rich red.
- Crystal Structure: Trigonal
Rubies are red sapphires since they are the red variation of corundum. Their intense red color has made them one of the most valuable gemstones in the world, with the term "pigeon's blood" denoting the most sought-after shade of red.
5. Chrysoberyl
- Hardness: 8.5 on the Mohs scale
- Colors Available: Yellow-green to green, though some varieties like alexandrite can show colors like red, green, and purple depending on the light.
- Crystal Structure: Orthorhombic
Chrysoberyl is an often-overlooked yet highly durable gemstone. It includes the fascinating alexandrite, known for its color-change properties, and the captivating cat's-eye chrysoberyl, which displays a striking chatoyancy effect.
6. Spinel
- Hardness: 8 on the Mohs scale
- Colors Available: Comes in a wide range of colors including red, pink, blue, and lavender.
- Crystal Structure: Cubic
Once mistaken for rubies and sapphires, spinel stands on its own as a coveted gemstone. Its hardness combined with a variety of beautiful colors and a cubic crystal structure makes it a durable and sparkling choice for jewellery.
7. Topaz
- Hardness: 8 on the Mohs scale
- Colors Available: Naturally colorless, but through impurities or treatment can be blue, green, yellow, orange, red, pink, and purple.
- Crystal Structure: Orthorhombic
Topaz is renowned for its hardness and rich color spectrum. It is often treated to create the popular blue topaz, but it's imperial variety—featuring a magnificent orange with pink undertones—is the most prized.
These seven gemstones are the royalty of durability in the gem world, prized not only for their ability to endure but also for their diverse and striking beauty. When choosing a gemstone for jewellery that will see everyday wear, considering one of these top contenders ensures a blend of beauty that lasts. Whether it’s the perfect diamond, a vibrant sapphire, or a gleaming piece of topaz, each of these minerals offers a unique combination of hardness and aesthetic appeal, perfect for a lifetime of adornment.