Three questions before daily wear

Durability is not one score. Hardness concerns resistance to scratches and abrasion. Toughness concerns resistance to breaking and chipping. Stability concerns response to conditions such as heat, light, chemicals and humidity. A material can perform strongly in one area while needing attention in another.

Start with the kind of risk you are considering. Contact between objects in a jewellery box raises a scratching question. A knock against a hard edge raises a breakage question. Strong light or a cleaning solution raises stability questions. Separating these situations is more useful than calling a gem simply strong or delicate.

Evidence: GIA: More than the Mohs scale

The Mohs scale is a ranking, not a ruler

The Mohs scale orders minerals by scratch resistance, from talc at 1 to diamond at 10. Its steps are not equal quantities. The difference between 9 and 10 is not the same as the difference between 4 and 5. Nor does a number describe resistance to every kind of damage.

Use the ranking to understand why storing gems together can create abrasion risks. Do not turn it into a home identification test by scraping a polished jewel against glass or another stone. A scratch test can leave permanent damage and still fail to answer the more complicated questions of identity, treatment or origin.

Evidence: GIA: Mohs scale and mineral hardness

Topaz: hardness does not remove cleavage

Topaz ranks 8 on the Mohs scale, yet its pronounced cleavage creates a vulnerability to splitting in a particular structural direction. A hard impact or sharp temperature change can cause breakage. This is not a contradiction: scratching a surface and separating a crystal are different events.

A cutter or setter considers orientation and protection. For the wearer, the lesson is to avoid using hardness alone as permission for rough activity. A topaz pendant and an exposed ring encounter different kinds of contact. Their suitability depends on the actual stone, mounting and use, rather than a number detached from its setting.

Evidence: GIA: topaz care cleaning

Two examples that overturn a simple ranking

Jadeite and nephrite have lower Mohs hardness than corundum, yet their interlocking structures give them exceptional toughness. They still need protection from scratches. This helps explain why a material can be well suited to carving while lacking diamond's resistance to abrasion.

Diamond illustrates the converse problem. It is extremely hard, but a sharp blow can still chip or fracture it. Exposed points, thin edges and pre-existing damage deserve attention. A diamond ring should not be treated as an indestructible tool. Neither a high hardness number nor a familiar advertising slogan eliminates the need to consider impact and the condition of the setting.

Evidence: GIA: jade care cleaning, GIA: Protecting diamond from chipping

Kunzite and opal: consider the environment

Kunzite can lose colour after prolonged exposure to intense light or heat. Its cleavage also demands care around impact and sudden temperature change. Keeping track of where an object is displayed can therefore matter as much as how gently it is handled.

Opal is another reminder that appearance and environment interact. High heat and abrupt temperature changes can cause fractures; heat from intense light can contribute to crazing, the network of fine cracks that may develop in some material. These facts are reasons for cautious storage and handling, not instructions to experiment with heat, soaking or chemicals to test authenticity.

Evidence: GIA: Kunzite care and cleaning, GIA: Opal care and cleaning

Assess the whole piece before cleaning

A jewellery item is more than its named centre stone. It may include smaller gems, surface treatments, adhesives, threads, old repairs or a vulnerable mounting. A cleaning method suitable for one component may be unsuitable for another. General material guidance cannot inspect those conditions remotely.

For an unfamiliar piece, record any existing chips or loose parts and ask a qualified professional about the entire object. Avoid ultrasonic or steam equipment until suitability is established. Removing a ring for strenuous or abrasive work and storing pieces separately are practical ways to reduce avoidable risk without attempting a material test.

Evidence: GIA: More than the Mohs scale, GIA: Protecting diamond from chipping, GIA: Opal care and cleaning

Self-check: name the risk before choosing a response

A polished surface rubs against a harder gem in a box. Which concept matters most? Hardness and abrasion. A topaz receives a sudden blow. Which concept matters? Toughness, including cleavage. A kunzite sits for months under intense display lighting. Which concept matters? Stability, including possible fading.

Now assess a hypothetical ring using three separate lines: scratching, impact, and environment. Add a fourth line for what is unknown about treatment and construction. If any line lacks evidence, do not fill it with the Mohs number. A useful durability assessment recognizes both what the material suggests and what still requires examination.

Evidence: GIA: Mohs scale and mineral hardness, GIA: topaz care cleaning, GIA: Kunzite care and cleaning