Don’t be fooled by everyday uses of the word “hard.” In the world of gemstones, hardness has a specific meaning. It’s all about how well a crystal resists scratches.

Imagine a fingernail easily scratching glass. In everyday terms, glass is hard. But for a gemologist, glass is relatively soft. Many materials considered hard in daily life can scratch gemstones.

Why is this so? It boils down to the atomic structure of the crystal. Strong bonds between atoms make it difficult to separate layers on the surface. A harder material can break these bonds, leaving a scratch.

The Mohs Scale: Ranking Crystal Toughness

To measure this “scratchability,” gemologists use the Mohs Scale. Developed in 1812, this system ranks ten common minerals based on hardness. Here’s the scale, with harder materials listed below:

  • Diamond (10)
  • Corundum (9)
  • Topaz (8)
  • Quartz (7)
  • Feldspar (6)
  • Apatite (5)
  • Fluorite (4)
  • Calcite (3)
  • Gypsum (2)
  • Talc (1)

The scale shows how scratches work. Each mineral can scratch those below it but gets scratched by those above. Minerals with the same hardness, like a ruby and sapphire, can’t scratch each other.

It’s interesting to note that the Mohs Scale isn’t perfectly linear. Hardness jumps significantly at higher numbers. Corundum is twice as hard as topaz, and diamond is four times harder than corundum! In fact, only diamonds can scratch other diamonds.

Precision and Challenges in Hardness Measurement

Gemstone hardness can vary slightly depending on its makeup and structure. Measuring it precisely can be tricky. Sometimes, what looks like a scratch might just be a mark left by a supposedly harder material.

Scientists use fractional scores (like 5.5) when necessary. But remember, the exact number isn’t as important as the general hardness range. This article covers the entire range you’ll find in gemology literature.

One exception is kyanite, a mineral with surprising hardness variations within a single crystal. But for most gemstones, hardness falls within a narrow range, typically differing by just one unit on the Mohs Scale.

Browse Crystals and Gemstones by hardness

All Crystals and Gemstones

Aqua Aura Quartz Meaning and Properties

Welcome to the mesmerizing world of Aqua Aura Quartz, a gemstone that's not just a feast for the eyes but a balm for the soul. Imagine holding a piece of the sky in your hands, its surface ...


The Mystical Origins of Amethyst Amethyst, a gemstone captivating hearts with its violet charm, has a name rooted in ancient Greek lore. The term 'amethyst' derives from the Greek words ...

Citrine: The Golden Gem of Light and Prosperity


Citrine is a variety of Quartz, silicon dioxide, the “common” form being heat-treated Amethyst. The color of this form can vary from pale yellow/gold to dark yellow/brown tones. Citrine usually ...

Tibetan Quartz Meaning and Properties

Tibetan Quartz Meaning and Properties

Tibetan Quartz is a unique variety of Colorless Quartz, also known as White Quartz or Rock Crystal, named for the Greek word 'krystallos,' meaning ice. Tibetan Quartz stands out for its stunning ...

Red Lace Agate

Red Lace Agate, as the name suggests, is known for its striking red color and intricate lace-like patterns. Each piece is a unique work of art, with bands, swirls, and zigzags creating a visual ...

Purple Lace Agate

Imagine a stone with the delicate intricacies of lace, lit from within by a radiant, royal hue. Envision a gem that combines natural elegance with a dash of human ingenuity, resulting in a unique, ...

Orange Lace Agate

Welcome to the fascinating world of gemstones and minerals, where every stone tells a story, a testament to the beauty and complexity of our natural world. Today, we delve into a unique gem that's ...

Brown Lace Agate

"Brown Lace Agate" - the name alone conjures images of intricately patterned bands of earthy brown hues, much like an exquisite piece of lace crafted by nature itself. However, here's a surprising ...

Yellow Lace Agate

Welcome, fellow gemstone enthusiasts, to the captivating world of Yellow Lace Agate - a delightfully vibrant variety of agate that captures the spirit of sunshine itself! This gemstone, ...

Pink Lace Agate

Let's delve into the intriguing enigma of Pink Lace Agate, a gemstone that sparks curiosity and admiration among collectors and jewelry enthusiasts worldwide. Agates, a distinctive category ...

Green Lace Agate

Have you ever heard of Green Lace Agate? If you're scratching your head, don't worry, you're not alone! As of the latest gemological updates, no such naturally occurring stone exists. Yet the notion ...

White Lace Agate

Envision it, if you will: a smooth, milky white surface, imbued with delicate, lace-like patterns, weaving a tapestry of soft swirls and curls. This could be the White Lace Agate, a gemstone that, ...

Black Lace Agate

Welcome to the intriguing world of gemstones, where every stone has a story to tell, and colors and patterns merge to create natural pieces of art. We're stepping off the well-trodden path to delve ...

Mexican Lace Agate

Mexican Lace Agate (also known as Crazy Lace Agate) is a variety of chalcedony renowned for its intricate lacy patterns and striking colors. Originates from the state of Chihuahua in Mexico, ...

Flower Lace Agate

Flower Lace Agate is an exquisite variety of banded Chalcedony, featuring intricate and floral lace-like patterns. These distinctive patterns are the outcome of ancient geological processes ...

Laguna Lace Agate

The Origin of Laguna Lace Agate Agates, with their remarkable play of colors and intrinsic patterns, have been fascinating rock-hounds for centuries. But among these geological gems, Laguna Lace ...

Ellensburg Blue Agate

Nestled in the heart of Washington State, in the charming town of Ellensburg, lies a hidden treasure that gem enthusiasts and history buffs alike will find irresistible. Known for its mesmerizing ...

Brazilian Agate

Brazilian Agate is a distinctive type of quartz known for its vibrant color patterns. These gemstones originate from the southern region of Brazil, more specifically, the region around Rio ...

Emoche ᛜ Gemstones & Jewelry