Peridot, a striking yellowish-green gemstone, is the gem-quality variety of the mineral olivine, often found in volcanic rocks and meteorites. This vibrant stone has a long history, with some of the oldest known specimens mined for the ancient Egyptians. The characteristic color of peridot comes from the iron content within its chemical structure. Peridot is classified as having a moderate hardness, typically ranking between 6.5 and 7 on the Mohs scale of mineral hardness.
Understanding Peridot’s Hardness on the Mohs Scale
The Mohs scale is a qualitative system that ranks a mineral’s resistance to scratching by comparing it to ten reference minerals. Developed in 1812, this ordinal scale runs from 1, represented by the softest mineral talc, up to 10, which is the hardness of diamond. It operates on the principle that any mineral can be scratched only by a material with a higher Mohs number.
Peridot’s position at 6.5 to 7 places it in a middle range, indicating a decent level of scratch resistance. This rating means it is harder than common metals like gold and silver used in jewelry settings.
However, peridot is similar in hardness to quartz, which is a major component of common household dust. Compared to much harder gems like sapphire or ruby (9) or diamond (10), peridot is considerably more vulnerable to surface damage. Exposure to dust and grit can cause small scratches and abrasions over time, meaning peridot requires more care than harder stones to maintain its brilliance.
Factors Affecting Peridot’s Practical Durability
While the Mohs rating addresses scratch resistance, a gem’s overall durability is also influenced by its tenacity and cleavage. Peridot has fair to good toughness, which is its ability to resist breaking, chipping, or cracking upon impact.
The stone has distinct cleavage, a tendency to split along specific planes of weakness when struck. This means a sharp blow could cause the peridot to chip or fracture more easily than its hardness suggests. The stone is also brittle, increasing its susceptibility to damage from mechanical stress.
Peridot is generally stable under normal light exposure, but it is chemically sensitive. It can be attacked by certain acids, and prolonged contact with acidic perspiration can cause surface damage. Rapid or uneven changes in temperature, known as thermal shock, can also induce internal fractures.
Recommendations for Wearing and Cleaning Peridot Jewelry
Given peridot’s moderate hardness and susceptibility to chipping along its cleavage planes, thoughtful wearing practices are recommended. Protective settings, such as bezels, are a better option for rings than more exposed prong settings, as they shield the stone’s vulnerable edges from accidental knocks.
Peridot is generally better suited for jewelry that receives less impact, such as pendants, brooches, or earrings.
It is advisable to remove peridot jewelry before engaging in activities that involve physical labor, contact with chemicals, or exposure to harsh abrasives. This includes:
- Gardening or exercising.
- Cleaning with household products.
- Swimming in chlorinated water.
Storing peridot pieces separately from harder gemstones like diamonds or sapphires is also important to prevent scratching.
For cleaning, the safest and most effective method is using warm, soapy water and a very soft brush. A gentle dish soap can be used to create a mild solution, allowing the jewelry to soak briefly. It is strongly advised to avoid mechanical cleaning devices like ultrasonic cleaners and steam cleaners. The intense vibrations or high heat can exacerbate existing flaws or cause new fractures due to the risk of thermal shock.