Hardness and toughness
Gem and mineral hardness is measured on the Mohs scale. The numbers are based on the relative ease or difficulty with which one mineral can be scratched by another. But the Mohs scale is deceptive. The steps between the minerals are not evenly spaced. For example, diamond is only one number away, but it’s many times harder than gems in the corundum family.
Peridot is 6.5 to 7 on the Mohs scale. It has fair to good toughness. Peridot is durable enough for jewelry wear but should be worn with some care so as not to scratch it or subject it to hard blows that can fracture it.
Rapid or uneven heat can cause peridot to fracture. Peridot is stable to light but is easily attacked by sulfuric acid, and less easily by hydrochloric acid. It can also be attacked over a long period of time by acid perspiration.
Warm, soapy water is the best method for cleaning peridot. Ultrasonic and steam cleaners are not recommended.