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.
Common substances like sand and dust are composed mostly of quartz, the mineral species that includes the variety citrine. So, while citrine is a great gemstone for use in jewelry, it should be treated with the proper care to prevent scratching and other damage.
Citrine rates a 7 on the Mohs scale and has good toughness, so it is suitable for all jewelry types. This includes rings as long as the wearer understands its limited hardness.