Mohs hardness scale: gemstone vulnerability

While diamonds may be considered gemstones that stand the tests of time, the same might not be said about softer gemstones such as fluorite, a beauty that would need more care and protection in a jewellery piece. Knowing a gemstones hardness is the key to all fine jewellery making, and the Mohs scale of hardness is a point of reference when deciding on which gemstones suit a bespoke jewellery item.

The Mohs scale was developed in 1812 by Friedrich Mohs, a German mineralogist, to indicate a minerals hardness by its ability to scratch one softer. In modern times, the Mohs scale has become a point of referral to describe a gemstones hardness, and is used to this day to determine what handmade jewellery piece can be fitted to which gemstone based on the gemstones durability and style.

As talc has a hardness of 1 according to the Mohs scale, talc cannot scratch a harder mineral such as gypsum or calcite—as is the way with all minerals, only a harder mineral can scratch a softer one. Although the Mohs scale orders ten gemstones on its list, there are many other gemstones that are represented by one of the ten above; that as it were, there are some variables, such as sapphires. Sapphires, as an example, are two times harder than topaz, yet four times softer than diamonds.

The Mohs scale, thus, simply orders a general list of a gemstone’s ability to scratch one softer, and not the toughness. While the hardness of a gemstone measures its durability against wear or surface corrosion, toughness measures its ability to withstand drops or heavy force. While diamonds are a 10 on the hardness scale, relating to its longevity in terms of scratching, diamonds don’t boast a particularly high toughness, meaning it is more likely to snap or shatter in certain circumstances.

Therefore, when choosing a gemstone for a bespoke piece of jewellery, the three foremost elements to consider is the style, value, and durability for its wear. As an example, topaz and emerald are high on the hardness scale but are considerably brittle—in jewellery, they would be worn best as earrings or pendants. Although the Mohs scale is used in reference, many combining factors are considered when creating a handcrafted item, making fine, carefully-constructed bespoke jewellery all the more desirable.