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Mohs hardness scale

The Mohs hardness scale, invented in 1812 by German mineralogist Friedrich Mohs, is a fundamental method for assessing the relative hardness of minerals and materials. It relies on a simple scratch test, where a material is scratched against a series of standard minerals with known hardness levels. The scale, ranging from 1 (the softest, talc) to 10 (the hardest, diamond), aids in mineral identification and comparison.

Over time, the Mohs scale has become a cornerstone in the jewelry and lapidary industries. Jewelers and lapidaries rely on it extensively when selecting gemstones, particularly when considering how the jewelry will be worn. This is because the Mohs scale provides crucial insights into a gemstone's durability, helping ensure that the chosen gem can withstand the intended wear and remain a cherished piece for years to come.


Hardness, as measured on the Mohs scale, is a property that depends on the strength of the atomic bonds within a crystal structure. This bonding strength is evident when pressure is applied to the surface layers of a material using another sample material. If the second material is harder than the first, it will leave a visible furrow or scratch on the surface. This phenomenon represents the breaking of countless atomic bonds on a microscopic scale. It's important to note that the Mohs scale primarily assesses the "scratchability" of materials, not their toughness or resistance to fracturing. For instance, diamond ranks as the hardest mineral with a Mohs value of 10, but it's not particularly tough; it can shatter when subjected to impact. This is captured by the popular saying: "If you hit a diamond with a hammer, it'll shatter into a dozen pieces. Hit a piece of quartz with a hammer, it'll split in two. Hit a piece of jade with a hammer, it'll ring like a bell!" This saying highlights the need for attention and care when handling diamonds, but it doesn't suggest they are weak or a poor choice. In fact, diamonds remain one of the best choices for jewelry due to their eternal luster and exceptional hardness. So, the Mohs scale is a tool primarily used for testing scratch resistance and evaluating a material's relative hardness.

10 - Diamond (The hardest mineral, can only be scratched by another diamond)

9 - Corundum (Sapphire and Ruby) (Extremely hard, can scratch most other minerals)

8 - Topaz (Very hard, can scratch quartz)

7 - Quartz (Hard, cannot be scratched by a knife)

7 - Tsavorites (Garnet) (Typically have a hardness of around 7 to 7.5, similar to quartz)

6.5 to 7 - Tanzanites  (Similar to or slightly harder than apatite)

6 - Orthoclase Feldspar (Moderately hard, can scratch glass)

5 - Apatite (Medium hardness, can scratch glass)

4 - Fluorite (Somewhat soft, can be scratched with a steel knife)

3 - Calcite (Moderately soft, can be scratched with a copper coin)

2 - Gypsum (Still quite soft, can be scratched with a fingernail)

1 - Talc (Very soft, can be easily scratched with a fingernail)

Game Changer

The invention of the Mohs hardness scale marked a transformative moment in the world of jewelry making and gemology. This ingenious scale rapidly emerged as an indispensable tool for mineralogists, geologists, and, notably, lapidaries – the artisans responsible for shaping and polishing gemstones for exquisite jewelry creations.

For lapidaries, the Mohs scale became a game-changer. It provided them with a straightforward means to determine the relative hardness of gemstones, aiding in the meticulous selection of materials for jewelry. Moreover, the scale played a pivotal role in distinguishing between colored gemstones, where visual similarities often posed challenges. By offering a method to verify gemstone identities, the Mohs scale revolutionized gemstone identification, facilitating the differentiation of similar-looking stones. While the Mohs scale didn't directly lead to the discovery of differences in colored gems of the same hue, its introduction significantly elevated the accuracy of gemstone identification, allowing for informed decisions based on hardness rather than appearance alone. In essence, the Mohs hardness scale has left an enduring legacy, empowering artisans and experts alike to craft exquisite jewelry and enhance our appreciation of the world's most beautiful gemstones.


Before the introduction of the Mohs hardness scale in the early 19th century, methods for assessing mineral hardness were primarily qualitative and subjective. Theophrastus, a renowned Greek philosopher who lived around 300 BCE, made pioneering contributions to early mineralogical knowledge while embodying a broader philosophical curiosity about the natural world. Known as the "Father of Botany" for his groundbreaking plant studies, Theophrastus's work on minerals, found in his treatise "Peri Lithon" or "On Stones," reflected his philosophical interest in understanding the natural world's intricacies. He qualitatively described various minerals and classified them based on properties like hardness, a system that laid the foundation for the systematic study of minerals and plants, bridging the realms of philosophy and the natural sciences. Friedrich Mohs in the 19th century later introduced a standardized and quantitative approach to measuring mineral hardness with his scale, marking a significant advancement in both mineralogy and the philosophy of science.


Gemstone hardness, as measured on the Mohs scale, plays a vital role in our relationship with stones and elements in everyday life. Whether we're selecting stones for everyday wear or heirloom jewelry, the Mohs scale serves as a guiding compass. When it comes to pieces meant for daily use, like rings, durability is of paramount importance. Diamond, with its unmatched Mohs hardness of 10, often takes the spotlight due to its exceptional toughness and resistance to scratches, even with frequent wear. However, on special occasions where jewelry is less exposed to wear and tear, gemstones like opals (with a Mohs hardness ranging from 5.5 to 6.5) can shine with their captivating play of colors. Yet, opals are also a prime example of how gemstone hardness matters. Their relatively softer nature makes them vulnerable to the abrasiveness of dust particles, which can gradually diminish their luster and brilliance over time. This underscores how everyday hazards, like seemingly harmless dust, accentuate the importance of considering gemstone hardness when both designing and wearing jewelry.

Storing Jewelry

When it comes to storing jewelry, gemstone hardness becomes a crucial factor in preserving the longevity and pristine condition of your treasured pieces. While it's generally advisable not to store jewelry together, especially during travel or within compartments, the importance of not mixing gems with significantly different hardness levels cannot be overstated. For example, storing a diamond ring alongside a sapphire ring is ill-advised due to the marked disparity in their Mohs hardness ratings. Diamonds, renowned for their exceptional hardness with a perfect score of 10, possess the potential to scratch the surface of sapphires, which rank slightly lower at 9 on the Mohs scale. This potential for abrasion underscores the utmost significance of thoughtfully pairing gemstones when storing your jewelry collection, ensuring that the inherent durability of each gem is meticulously preserved.

Heirloom & Fashion

The Mohs hardness scale profoundly influences the choice of gemstones for heirloom and fashion jewelry, providing valuable guidance for both enduring legacies and fleeting moments of beauty. Heirloom pieces, intended to withstand the test of time, rely on the Mohs scale as a reliable compass, directing us toward gemstones with the durability to span generations. Diamonds, boasting an unwavering Mohs rating of 10, and corundum, rubies and sapphires, scoring a 9 make prime choices for heirloom pieces. 

In the realm of fashion jewelry, marked by its ever-evolving trends and the passionate pursuit of individuality and self-expression, softer stones find their rightful niche. Among these gems are the rare and enchanting ones, like opals and tanzanites, boasting captivating optical properties. While these softer stones do have the potential to evolve into heirlooms, they demand meticulous attention and care, making them particularly suited for pendants and earrings, rather than rings. They make stunning choices for special occasions, allowing wearers to make a distinct and captivating statement in the realm of fashion and luxury.


The Mohs hardness scale, while valuable in many applications, has limitations that make it less ideal for certain purposes, such as detailed scientific mineralogical analysis. One limitation is its qualitative nature, providing relative rankings of hardness rather than precise measurements. Additionally, it doesn't account for variations within a mineral species or factors like crystallography, which can influence hardness. Despite these limitations, the Mohs scale persists in jewelry for its simplicity and practicality. It's an easy-to-use tool that quickly assesses the relative durability of gemstones, aiding jewelers and consumers in making informed choices.

An alternative to the Mohs scale is the Vickers hardness test, which provides a quantitative measure of hardness by indenting a material with a standardized diamond-shaped indenter and measuring the resulting impression's dimensions. This test is more precise and applicable in materials science and engineering contexts. However, in the world of jewelry, where simplicity and quick assessments are often more relevant, the Mohs scale remains a practical choice.

The Mohs hardness scale retains its central role in the world of jewelry. Its simplicity and practicality empower us to make well-informed choices when selecting gemstones, whether for timeless heirlooms or for celebrating moments of personal style and expression. This enduring tool not only assists in the careful placement of gemstones but also underlines our enduring fascination with Earth's precious treasures, which hold unique value in diverse jewelry creations.

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